Stacking UM/UIM Coverage in Pennsylvania: What Injured Drivers Need to Know
When an uninsured or underinsured driver leaves you with catastrophic injuries, Pennsylvania's stacking rules can multiply your available coverage—but only if you didn't waive that right when you bought your policy. Here's how stacking works, what it costs, and why it matters after a serious collision.
Stacking UM/UIM Coverage in Pennsylvania: What Injured Drivers Need to Know
A Reading woman suffered a fractured pelvis and traumatic brain injury when a pickup truck ran a red light on Route 222, according to Pennsylvania State Police. The at-fault driver carried Pennsylvania's minimum liability limit: $15,000 per person. Her medical bills topped $240,000 within the first month. She owned three vehicles, each insured under the same policy with $100,000 in uninsured/underinsured motorist (UM/UIM) coverage. Because she had purchased stacked UM/UIM, she could access $300,000—three times the per-vehicle limit—to bridge the gap the negligent driver's policy couldn't cover. Had she opted for non-stacked coverage to save $60 per year, her maximum UM/UIM recovery would have been $100,000, leaving a $125,000 shortfall she would bear alone.
Stacking is one of the least-understood but most financially consequential choices Pennsylvania drivers make when they sign an auto-insurance application. This guide explains what stacking is, how Pennsylvania law treats it, when it applies, what it costs, and how to preserve your right to stack before an accident happens.
What UM/UIM Coverage Does (And Why Pennsylvania Requires It)
Uninsured motorist (UM) coverage pays for your injuries when a driver with no liability insurance causes a crash. Underinsured motorist (UIM) coverage kicks in when the at-fault driver has insurance, but their policy limit is too low to fully compensate your damages. Under 75 Pa.C.S. § 1731, every Pennsylvania auto policy must offer UM and UIM coverage in amounts equal to your liability limits unless you reject it in writing.
Pennsylvania's minimum required liability is $15,000 per person and $30,000 per accident (often written 15/30/5). According to the Insurance Research Council, roughly one in eight Pennsylvania drivers operates without any liability insurance. Among those who are insured, a significant percentage carry only the statutory minimum. When a $15,000 policy meets a $200,000 spinal-fusion surgery, UM/UIM coverage becomes the victim's primary financial lifeline.
UM/UIM is first-party coverage: you collect from your own insurer, not the at-fault driver's carrier. Your insurer then pursues subrogation against the negligent party. Because you're dealing with your own carrier—an entity with which you have a contractual relationship—the claims process often moves faster than a third-party liability claim, though disputes over policy limits and stacking waivers do arise.
Stacked vs. Non-Stacked: The Core Distinction
Pennsylvania law presumes that UM/UIM coverage is stacked unless the policyholder signs a written waiver selecting non-stacked (or "unstacked") coverage. The distinction centers on whether you can combine ("stack") the per-vehicle UM/UIM limits from multiple vehicles on the same policy—or from multiple policies covering vehicles you own or regularly use.
Stacked Coverage
With stacked UM/UIM, your available coverage equals the per-vehicle limit multiplied by the number of insured vehicles. If you own two cars, each with $50,000 in UM/UIM, you have access to $100,000 in total UM/UIM protection. Own four vehicles at $100,000 each? Your stacked limit is $400,000. This multiplication applies whether you're injured in one of your own vehicles, riding as a passenger in someone else's car, or even struck as a pedestrian.
Stacking comes in two flavors:
- Intra-policy stacking: combining limits across multiple vehicles on the same policy.
- Inter-policy stacking: combining limits across separate policies where you are a named insured or resident relative (for example, your personal policy plus a spouse's separate policy, or coverage on a vehicle you own and a vehicle owned by a household member).
Pennsylvania courts have consistently upheld the right to stack across both dimensions unless a valid waiver exists.
Non-Stacked Coverage
Non-stacked UM/UIM caps your recovery at the per-vehicle limit regardless of how many vehicles you insure. If you carry $100,000 non-stacked on three vehicles, the maximum UM/UIM benefit is $100,000—not $300,000. Insurers charge lower premiums for non-stacked coverage because their maximum exposure per claim is fixed at the single-vehicle limit.
The waiver must be "knowing, intelligent, and voluntary." Courts have invalidated waivers that were ambiguous, buried in fine print, or signed without a clear explanation. In Craley v. State Farm, the Pennsylvania Supreme Court held that the insurer bears the burden of proving a valid waiver and that any ambiguity is construed against the insurer.
How Stacking Works in Real Scenarios
Consider three common fact patterns:
| Scenario | Your UM/UIM Election | Vehicles Insured | Per-Vehicle Limit | Available UM/UIM |
|---|---|---|---|---|
| You own two cars on one policy | Stacked | 2 | $50,000 | $100,000 |
| You own two cars on one policy | Non-stacked | 2 | $50,000 | $50,000 |
| You and your spouse each own a car; separate policies | Stacked (both policies) | 2 (one per policy) | $100,000 each | $200,000 |
| You own three vehicles on one policy | Stacked | 3 | $100,000 | $300,000 |
| You own three vehicles on one policy | Non-stacked | 3 | $100,000 | $100,000 |
Example: Multi-Vehicle Household
A Pittsburgh family insures a sedan, an SUV, and a minivan under a single policy. Each vehicle carries $100,000/$300,000 liability and $100,000 UM/UIM stacked. The father is rear-ended by a driver with a $15,000 policy while driving the sedan. His medical bills, lost wages, and pain-and-suffering total $180,000. He exhausts the at-fault driver's $15,000 liability, leaving $165,000 unpaid. Because he elected stacked UM/UIM, he can access $300,000 in underinsured-motorist coverage (three vehicles × $100,000), easily covering the shortfall. Had he chosen non-stacked to save approximately $150 annually in premium, his UM/UIM cap would have been $100,000, and he would absorb a $65,000 loss out-of-pocket.
Example: Pedestrian Struck by Uninsured Driver
An Allentown woman is struck in a crosswalk by an uninsured driver. She suffers a femur fracture requiring surgery. She owns one vehicle with $50,000 stacked UM coverage and is also a named insured on her husband's policy covering two vehicles at $50,000 stacked UM each. She can stack across both policies: $50,000 from her own policy plus $100,000 from her husband's (two vehicles × $50,000), for a total of $150,000 in UM protection. If both policies were non-stacked, she would be limited to $50,000 from her own policy.
The Legal Foundation: Pennsylvania Statutes and Case Law
Pennsylvania's UM/UIM framework sits in the Motor Vehicle Financial Responsibility Law (MVFRL), codified at 75 Pa.C.S. § 1701 et seq. Section 1731 mandates that insurers offer UM/UIM equal to the insured's liability limits and that the coverage is stacked unless the insured signs a written waiver.
Key appellate decisions have shaped how stacking works in practice:
- Gallagher v. Geico: The Pennsylvania Supreme Court clarified that inter-policy stacking is available when the insured is a named insured or resident relative on multiple policies, even if issued by different carriers.
- Craley v. State Farm: Held that the insurer must prove a valid waiver by clear and convincing evidence. Ambiguous policy language is construed in favor of stacking.
- Majority opinion in MVFRL cases: Pennsylvania courts favor stacking as the default rule. Any limitation must be explicit, conspicuous, and voluntarily accepted by the policyholder.
Because Pennsylvania law presumes stacking, insurers typically include a dedicated waiver form—often a separate page titled "Waiver of Stacked Uninsured/Underinsured Motorist Coverage"—that the applicant must initial and sign. Online quote platforms often present this as a checkbox or drop-down menu; the legal effect is the same if the electronic signature meets Pennsylvania's requirements.
How Much Stacking Costs (And Whether It's Worth It)
Carriers price non-stacked UM/UIM lower because their maximum per-claim payout is capped at the single-vehicle limit. Stacked premiums reflect the insurer's increased exposure.
For a household insuring two vehicles in Pennsylvania, the annual premium difference between $100,000 stacked and $100,000 non-stacked UM/UIM typically ranges from $40 to $120, depending on the insurer, your driving record, and geographic rating territory. For three vehicles, the spread widens to $80–$200 annually. Higher UM/UIM limits (e.g., $250,000 or $500,000) produce larger absolute differences but often shrink on a percentage basis because base rates for higher limits already incorporate lower per-dollar risk.
Cost-Benefit Analysis
Consider a household with three vehicles, each carrying $100,000 UM/UIM:
- Stacked premium: approximately $180 more per year than non-stacked.
- Benefit: access to $300,000 in UM/UIM instead of $100,000—a $200,000 increase in protection.
- Break-even: even one moderate-severity claim (e.g., a broken bone with surgery and three months of lost wages) can exceed $100,000 in total damages. The additional $180 annually buys $200,000 of extra coverage—a 1,111-to-1 return if that coverage is ever needed.
For most households, stacking is a prudent investment. The premium difference is modest, and the financial protection is exponential. Single-vehicle households see less benefit (because there's nothing to stack), but households with two or more vehicles should default to stacked unless budget constraints are severe.
Common Pitfalls and How to Avoid Them
Many Pennsylvania drivers unknowingly waive stacking or misunderstand how it applies. Here are the most frequent mistakes:
1. Signing the Waiver Without Reading It
Insurers are required to offer stacked UM/UIM, but they're also permitted to offer a lower premium for non-stacked. Sales agents—particularly those compensated by commission—may emphasize the cost savings without fully explaining the coverage trade-off. Always ask, "What happens if I'm hit by someone with minimum coverage?" before you sign.
2. Assuming You Can Stack After an Accident
You cannot retroactively elect stacking after a crash. The choice must be made before the policy period during which the accident occurs. If you're currently non-stacked, contact your agent to switch to stacked now—it will apply to accidents that happen after the endorsement takes effect.
3. Believing One Vehicle Means No Stacking
A single-vehicle household cannot intra-policy stack, but if you're a named insured or resident relative on another household member's policy—or if you have a separate policy on a motorcycle or recreational vehicle—you may be able to inter-policy stack. Review all policies in your household.
4. Overlooking Household Vehicles
Pennsylvania courts have held that resident relatives can stack UM/UIM across all household policies unless each policy contains a valid anti-stacking waiver. If your spouse drives a vehicle titled solely in their name and insured separately, and both policies are stacked, you can combine limits when injured.
5. Confusing UM/UIM Stacking With Medical-Benefits Stacking
Pennsylvania also requires first-party medical benefits (often $5,000 minimum). These benefits are not stackable in the same way. UM/UIM stacking is a separate election. Don't conflate the two.
What to Do If Your Claim Involves Stacking
If you're injured by an uninsured or underinsured driver and you believe you have stacked UM/UIM, follow these steps:
- Notify your own insurer immediately. UM/UIM is a first-party claim. The at-fault driver's lack of adequate coverage triggers your policy.
- Request copies of all relevant policies. Gather declarations pages and waiver forms (or lack thereof) for every vehicle you own or regularly use, plus any household policies.
- Identify all potential sources of UM/UIM. If you're a named insured on your own policy and a resident relative on your parents' or spouse's policy, both may be stackable.
- Quantify your damages carefully. UM/UIM claims require proof of medical expenses, lost income, and non-economic damages (pain and suffering). Because you're claiming against your own carrier, thorough documentation is critical.
- Engage a Pennsylvania injury attorney early. Insurers sometimes dispute stacking eligibility, the validity of waivers, or the calculation of damages. An attorney can review your policy language, research case law, and negotiate or litigate the claim.
Pennsylvania law also permits UM/UIM arbitration when the parties dispute the amount of damages but agree that coverage exists. Arbitration is faster and less expensive than a jury trial, but the decision is binding within certain limits.
How Stacking Interacts With Other Pennsylvania Insurance Rules
Pennsylvania's "choice no-fault" system adds layers of complexity. Under 75 Pa.C.S. § 1705, policyholders choose between limited tort (which waives the right to sue for pain and suffering unless a "serious injury" threshold is met) and full tort (which preserves all common-law damages rights). This election does not affect UM/UIM entitlement—you still collect UM/UIM benefits under either tort option—but it does influence the scope of damages you can recover from the at-fault party and, by extension, the size of the UIM claim.
If you elected limited tort and your injuries don't qualify as "serious," your third-party recovery from the at-fault driver is capped at economic losses (medical bills and lost wages). However, your UM/UIM claim can still cover those economic losses when the at-fault driver is uninsured or underinsured. The stacking question determines how much UM/UIM money is available, not what damages it covers.
Coordination With Medical Benefits
Pennsylvania's first-party medical benefits (sometimes called "med pay" in other states) pay a portion of your medical bills regardless of fault. These benefits are exhausted before you tap UM/UIM. For example, if you have $5,000 in medical benefits and $50,000 in medical bills, your insurer pays the first $5,000 under medical benefits, and you pursue the remaining $45,000 (plus lost wages and pain-and-suffering) through the at-fault party's liability policy or your UM/UIM.
Subrogation and Reimbursement
When you collect UM/UIM benefits, your insurer typically gains subrogation rights against the at-fault driver. If your UM/UIM carrier pays $100,000 and you later recover $15,000 from the negligent driver's minimum-limits policy, your insurer is entitled to reimbursement up to the amount it paid. Pennsylvania law also addresses the "made-whole" doctrine: in some cases, the insurer cannot enforce subrogation until you've been fully compensated.
Special Situations: Commercial Policies, Named Non-Owner Coverage, and Motorcycles
Commercial Auto Policies
Business-owned vehicles can carry UM/UIM, but Pennsylvania law treats commercial policies differently in some respects. Stacking may be available depending on policy language and whether the vehicles are scheduled separately. If you're injured while driving a company vehicle, review both your employer's commercial policy and your personal auto policy—you may be able to stack your personal UM/UIM with the employer's coverage if you're a named insured on your own policy.
Named Non-Owner Policies
A named non-owner policy provides liability and UM/UIM for individuals who don't own a vehicle but drive regularly (e.g., someone who borrows a family member's car or uses a car-share service). These policies typically cannot be stacked with the owner's policy unless the non-owner is also a named insured or resident relative on that policy. However, the UM/UIM on a non-owner policy can provide excess coverage after the owner's policy is exhausted.
Motorcycle and Recreational-Vehicle Policies
Motorcycles are considered motor vehicles under Pennsylvania law and must carry UM/UIM unless waived. Motorcycle UM/UIM can often be stacked with auto UM/UIM if both policies are stacked and the insured qualifies as a named insured or resident relative on each. Pennsylvania has seen several appellate cases affirming inter-policy stacking between a motorcycle policy and a passenger-car policy.
Should You Buy Higher UM/UIM Limits?
Even with stacking, the total available UM/UIM depends on your per-vehicle limit. A household with three vehicles at $25,000 UM/UIM stacked can access $75,000—still insufficient for a traumatic brain injury or spinal-cord case. Increasing your per-vehicle UM/UIM to $100,000, $250,000, or $500,000 has two effects:
- Higher per-vehicle protection: if you insure only one vehicle, or if you're injured while a passenger in someone else's car (where stacking may not apply), a higher single limit provides better coverage.
- Higher stacked total: three vehicles at $250,000 each provide $750,000 stacked—enough to cover many catastrophic-injury claims that exceed a defendant's minimum-limits policy.
Premium increases for higher UM/UIM are not linear. Doubling your limit from $50,000 to $100,000 typically increases premium by 30–50 percent, not 100 percent, because insurers price higher limits at lower per-dollar rates (reflecting the reduced frequency of claims that exhaust higher limits). Umbrella policies generally do not cover UM/UIM gaps, so raising your auto UM/UIM is the only way to increase this protection.
When Non-Stacked Might Make Sense (Rarely)
For a small subset of drivers, non-stacked coverage is a defensible choice:
- Single-vehicle households: if you own only one car, there's no intra-policy benefit to stacking (though inter-policy stacking with a household member's policy could still apply).
- Very tight budgets: if the premium difference forces a choice between carrying any UM/UIM or dropping coverage entirely, non-stacked is better than none.
- High-net-worth individuals with alternative protection: someone with substantial assets, disability insurance, and health insurance may choose non-stacked to minimize premium and self-insure the gap—but this is rare and generally unwise, because UM/UIM claims can reach seven figures in severe-injury cases.
For the vast majority of Pennsylvania households—especially those with two or more vehicles—stacked UM/UIM is the superior choice. The modest premium pays for exponentially greater protection when you need it most.
Key Takeaways
- Stacking multiplies your UM/UIM coverage by the number of vehicles you insure, providing critical protection when an at-fault driver is uninsured or carries only Pennsylvania's low minimum limits.
- Pennsylvania law presumes stacked coverage unless you sign a written waiver. If you're unsure whether you waived stacking, request a copy of your policy and all signed forms from your agent.
- The premium difference is modest—typically $40–$200 annually for a multi-vehicle household—while the benefit can exceed $100,000 or more in a serious-injury claim.
- You cannot elect stacking retroactively. If you're currently non-stacked, contact your insurer today to switch; the change applies only to future accidents.
- Stacking works across policies if you're a named insured or resident relative on more than one policy, including a spouse's or parent's separate policy.
- Review your coverage annually, especially if you add vehicles, household members marry or divorce, or you move to a new rating territory.
- Higher per-vehicle UM/UIM limits increase your stacked total. Consider $100,000 or $250,000 per vehicle instead of the minimum.
Get Matched With a Pennsylvania Injury Lawyer Who Understands UM/UIM Claims
Disputes over stacking, policy interpretation, and damages calculation are common in UM/UIM cases. Insurers sometimes deny that a valid waiver exists, argue that household policies cannot be stacked, or undervalue your claim. Because you're pursuing benefits from your own carrier—an entity with which you have a contractual relationship and which may prioritize claim-cost control—having an attorney review your policy and advocate for full recovery is essential.
PennsylvaniaAccidentAid.com connects injured Pennsylvanians with experienced local attorneys who handle Car Accidents, Truck Accidents, Motorcycle Accidents, and other serious-injury claims involving UM/UIM. The platform is free to use, and there's no obligation. Simply describe your situation, and we'll match you with attorneys in Philadelphia, Pittsburgh, Allentown, Erie, or your area who can evaluate your stacking rights, quantify your damages, and pursue every dollar you're owed. Pennsylvania's two-year statute of limitations (42 Pa.C.S. § 5524) means that waiting can forfeit your claim—reach out today to protect your rights and your financial future.
Related Pennsylvania Guides
- Inter-Policy Stacking in Pennsylvania After Donovan v. State Farm
- What Your Pennsylvania Auto Insurance Limits Actually Mean (And Why They Matter)
- Uninsured Motorist (UM) Claims in Pennsylvania: When the Other Driver Has No Coverage
- Underinsured Motorist (UIM) Claims in Pennsylvania: A Complete Guide
- Gap Insurance and Financed Vehicles After a Pennsylvania Total Loss
Frequently asked questions
What does it mean to stack UM/UIM coverage in Pennsylvania?
Stacking allows you to combine (or 'stack') the uninsured and underinsured motorist coverage limits from multiple vehicles on your policy—or across separate policies where you're a named insured or resident relative. For example, if you own three vehicles each with $100,000 in UM/UIM and you elected stacked coverage, your total available UM/UIM is $300,000, not just $100,000. This multiplied protection is crucial when an at-fault driver has no insurance or carries only Pennsylvania's minimum $15,000 liability limit and your injuries exceed that amount. Stacking is the default under Pennsylvania law unless you sign a written waiver choosing non-stacked coverage.
How much does stacked UM/UIM cost compared to non-stacked in Pennsylvania?
The annual premium difference typically ranges from $40 to $200 depending on the number of vehicles, your chosen UM/UIM limit, your insurer, and your geographic rating area. For a two-vehicle household with $100,000 UM/UIM, stacked coverage usually costs $60 to $120 more per year than non-stacked. For three vehicles, the spread might be $100 to $200 annually. While non-stacked premiums are lower, the trade-off is significant: non-stacked caps your UM/UIM recovery at the single-vehicle limit regardless of how many cars you insure, leaving you financially exposed if your injuries exceed that amount. Most households find the modest premium increase worthwhile for the exponentially greater protection stacking provides.
Can I change from non-stacked to stacked coverage after an accident?
No. You cannot retroactively elect stacked coverage after a crash has occurred. The stacking election you made when you purchased or last renewed your policy governs the accident. If you're currently carrying non-stacked UM/UIM and want the protection of stacked coverage, you must contact your insurance agent or carrier immediately to request the change; it will apply only to accidents that happen after the endorsement takes effect. Pennsylvania law requires insurers to offer stacked coverage by default, but many drivers unknowingly waive it by signing a non-stacked election form to lower their premium. Review your declarations page and contact your agent today if you're unsure which option you selected.
Does Pennsylvania require UM/UIM coverage on every auto policy?
Yes, under 75 Pa.C.S. § 1731, every auto insurance policy issued in Pennsylvania must include uninsured and underinsured motorist coverage in amounts at least equal to your liability limits, unless you reject it in writing. The law also presumes that UM/UIM is stacked unless you sign a specific waiver electing non-stacked coverage. Because roughly one in eight Pennsylvania drivers is uninsured and many others carry only the state's low $15,000-per-person minimum, UM/UIM is often your most important financial protection after a serious crash. Rejecting UM/UIM entirely or choosing very low limits can leave you personally responsible for tens or hundreds of thousands of dollars in medical bills and lost income if an uninsured driver injures you.
Can I stack UM/UIM across policies from different insurance companies?
Yes, Pennsylvania law permits inter-policy stacking—combining UM/UIM limits from separate policies—if you are a named insured or resident relative on each policy. For example, if you have a personal auto policy with $100,000 stacked UM/UIM and your spouse has a separate policy (even with a different carrier) covering two vehicles at $50,000 stacked each, you may be able to stack across all three vehicles for a total of $200,000 in UM/UIM protection. The key requirement is that both policies must have valid stacked elections and you must qualify as an insured under each. Courts have consistently upheld inter-policy stacking as long as no valid anti-stacking waiver exists.
What happens if my insurer says I waived stacking but I don't remember signing anything?
Pennsylvania law places the burden on the insurance company to prove that you signed a knowing, intelligent, and voluntary waiver of stacked coverage. In disputes, courts scrutinize whether the waiver form was clear, conspicuous, and properly explained. Ambiguous policy language or waivers buried in fine print have been invalidated in Pennsylvania appellate cases. If your insurer claims you elected non-stacked but cannot produce a signed waiver or the waiver language is unclear, you should immediately consult a Pennsylvania injury attorney who can review your policy documents and challenge the waiver. Successfully proving the absence of a valid waiver can restore your right to stack and substantially increase the UM/UIM benefits available for your claim.
Does stacking apply if I'm injured as a passenger or pedestrian?
Yes. Stacked UM/UIM coverage follows you as an insured person, not just the vehicle. If you're injured as a passenger in someone else's car, or even struck as a pedestrian or cyclist by an uninsured or underinsured driver, you can claim UM/UIM benefits under your own stacked policy. If you own three vehicles with $100,000 stacked UM/UIM, you have access to $300,000 in coverage regardless of whether you were driving your own car, riding in a friend's vehicle, or walking across the street. This portability is one of the most valuable features of stacked coverage and a key reason why households with multiple vehicles should elect stacking.
How do I know if I have stacked or non-stacked UM/UIM coverage?
Check the declarations page of your auto insurance policy. It will list your UM/UIM limits per vehicle and indicate whether the coverage is 'stacked' or 'non-stacked' (sometimes written as 'unstacked'). If you're unsure, contact your insurance agent and ask them to confirm your election in writing. You can also request a copy of any waiver forms you signed when you purchased the policy. If your declarations page shows identical UM/UIM limits for each vehicle without a notation about stacking, or if you never recall being offered a choice, you should assume you have stacked coverage (since that is Pennsylvania's default) but verify with your insurer to be certain. Understanding your coverage before an accident is critical.
Can I stack UM/UIM if I only own one vehicle?
Generally no—if you insure only one vehicle on your own policy, there is nothing to 'stack' within that single policy (no intra-policy stacking). However, you may still benefit from inter-policy stacking if you are a named insured or resident relative on another household member's policy, such as a spouse's or parent's separate auto policy. For example, if you own one car with $100,000 UM/UIM and your spouse owns a separate vehicle with its own $100,000 UM/UIM policy, you might be able to stack across both policies for a combined $200,000. Single-vehicle households should still elect stacked coverage in case they later add a vehicle or to preserve the option of inter-policy stacking with household members' coverage.
What is the difference between UM and UIM coverage in Pennsylvania?
Uninsured motorist (UM) coverage pays when the at-fault driver has no liability insurance at all, or when you're the victim of a hit-and-run and the driver cannot be identified. Underinsured motorist (UIM) coverage applies when the at-fault driver does carry liability insurance, but their policy limit is too low to fully compensate your damages. For example, if your medical bills and lost wages total $150,000 and the negligent driver has only Pennsylvania's minimum $15,000 liability, you can collect that $15,000 from the at-fault party, then turn to your own UIM coverage for the remaining $135,000 (up to your UIM limit). Both UM and UIM are first-party coverages paid by your own insurer, and both are stackable under the same rules.