You know that moment. It’s 95 degrees outside, you’re parked in full sun, and the AC kicks on. The first blast of air smells like a mix of stale dust and whatever died in the ductwork last season. You pull the filter and it’s gray-brown, sagging, and honestly, you’re not sure the last time it was actually clean.
That was me last June. I had three different filter sizes because my rig has two AC units and neither takes the same size. The OEM replacements cost like $20 each plus shipping. For foam. That’s criminal.
So I rolled the dice on this 16 x 40 x 1/4-inch sheet from a brand I’d never heard of. $13 bucks. Worst case, I’m out the price of a six-pack.
Turns out, it’s the most sensible filter purchase I’ve made in years. Here’s the honest breakdown.
What You’re Actually Getting
The package is one big sheet of open-cell polyurethane foam. 16 inches by 40 inches, quarter-inch thick. You cut it to fit whatever your AC unit needs. That’s the whole product. No fancy frame, no adhesive backing, no pre-cut perforations.
Which sounds stupidly simple, but let me tell you why that simplicity matters:
One size fits most. I cut two filters from a single sheet. One for my Dometic roof unit, one for the mini-split intake. If I’d bought OEM, I’d have paid double and still had to wait for shipping.
The foam density is right. Not too stiff, not cheesecloth-thin. When you hold it up to light, you can see the pore structure — enough to catch dust and pollen without strangling airflow. Some cheap filters are so densely packed they turn your AC into a whisper and your RV into a sauna. This one breathes.
It washes clean. I’ve hosed mine off three times now. Let it dry in the sun, and it’s back to white-ish. The $13 price tag stings less when the filter lasts two seasons.
Cutting the Damn Thing
The listing says ‘can cut to fit.’ That’s technically true but undersells the experience. You know what’s the absolute worst part of RV maintenance? Anything that requires precision. If you’re like me, you’ve got scissors that are dull, a utility knife that’s seen better days, and a workbench that doubles as the dinette table.
Here’s the trick: lay the filter on a flat surface, put your old filter on top as a template, and trace around it with a marker. Then use sharp scissors — not your kitchen shears, don’t do that to your marriage — and cut about a quarter inch outside the line. The foam compresses when you slide it into the frame, so you want it slightly oversized.
My first cut was a little wonky on one corner. Didn’t matter. The foam squished into place and sealed fine. You don’t need precision here, just close enough.
If you’re replacing the filter in a rooftop unit, you’ll want to pop the ceiling shroud off first. That part’s annoying — four screws, some sealant you’ll need to redo — but the filter sits right there under the intake grille. Takes ten minutes total.
Airflow and Performance
Here’s the thing nobody tells you about RV AC filters: the right filter barely affects how cold the air feels. It’s all about keeping the coils clean. A dirty coil means the compressor runs hotter, uses more power, and eventually dies. That’s a $1,200 repair. This filter costs less than a tank of gas.
I’ve run my AC hard all summer — full sun, 100 degree heat, the works. Pulled the filter at the end of August and the coils underneath were almost spotless. That’s the proof right there.
Airflow-wise, I didn’t notice any drop when I swapped from the OEM filter. The quarter-inch thickness is fine for most residential-style foam filters. If you have one of those ultra-high-MERV pleated filters, this will let more dust through, no question. But in an RV, you’re not dealing with allergies and fine particulate the way you would in a house. You’re dealing with road dust, pollen, and the occasional bug that finds its way in. Open-cell foam handles that.
The Mini-Split Connection
Now, if you’ve upgraded your rig to something more modern — and I know a few of you have been eyeballing it — you might wonder if this filter matters.
I installed a YITAHOME 18000 BTU Mini Split AC/Heating System in my workshop last spring, and it comes with a washable mesh filter that’s honestly pretty decent. But the foam sheets work just as well if you need a backup or want to add a layer of pre-filtering on the intake. I cut a piece for the return air grille on the indoor unit and it catches the big stuff before it hits the mesh. That means the mesh stays cleaner longer, which means the coil stays cleaner, which means the unit runs more efficiently.
If you’re still rocking a rooftop unit, the same logic applies. Actually, there’s a whole discussion about whether to stick with rooftop or switch to a mini-split for quiet operation — the TURBRO Inverter 13.5K BTU RV Air Conditioner is a solid option if you’re replacing the whole thing. But whatever you run, cheap foam filters are the cheap insurance that keeps the expensive part alive.
The ‘Genuine OEM’ Scam
Let’s talk about the elephant in the room. The manufacturer wants you to believe that only their filters are safe. ‘Genuine part,’ ‘factory spec,’ ‘optimal performance.’ It’s all marketing garbage. These foam filters are a commodity. The OEM is buying the same open-cell polyurethane from a supplier, putting it in a branded box, and charging you 300% markup.
The only spec that matters on an AC filter is the pore size, which determines how much dust you catch versus how much air flows through. This filter’s pore structure is visually indistinguishable from the OEM. I’d bet money they come from the same factory in China.
Now, if your unit is still under warranty, maybe play it safe and use OEM until the warranty expires. I get it, warranties are finicky. But after that? Buy the cheap stuff. Your AC doesn’t care what brand the foam is. It cares that the coil isn’t caked in dust.
Sizing and Fit Notes
The sheet is 16 x 40. That’s big enough for most RV AC units, but let’s do the math before you buy. Measure your current filter. If it’s larger than 16 x 40, this won’t work — though I’ve never seen a residential RV unit that needs more. If it’s smaller, you’re golden. You can get two or three filters out of one sheet depending on your size.
For the standard Dometic and Coleman rooftop units, the filter is typically around 13 x 20 or so. One sheet gives you two replacements. At $13, that’s $6.50 per filter. Compare that to the $15-25 you’d pay for OEM. You’re saving money on the thing you’re supposed to replace every few months.
The quarter-inch thickness is worth noting. Some units have a filter slot that’s a bit deeper — maybe three-eighths or half an inch. The foam compresses, so it still works, but you might want to stack two layers if you have a really thick slot. I doubled up on one of my units and it was snug but fine.
What Could Be Better
I’m not going to pretend this is perfect. It’s not. Here’s what bugged me:
The first wash was messy. The foam holds dust like a magnet, so when you rinse it, the water runs brown. That’s expected, but you need to do it outside or over a drain. Don’t wash it in the kitchen sink unless you want to explain to your partner why the sink looks like you’re dealing with a crime scene.
No markings for cutting. The sheet is blank. If you’re someone who likes grid lines or perforations to guide your cut, you’ll be freehanding it. I used the old filter as a template, which worked fine, but I can see someone struggling if they’re replacing a filter they don’t have anymore. Measure twice, cut once, all that.
It’s thin. Some people are going to look at this and think it won’t catch anything. It will. But if you’re the type who wants a rigid frame around the filter, this isn’t that. It’s a floppy sheet of foam. You slide it in, the grille holds it in place, done.
One sheet, not a pack. The listing is for a single sheet. At $12.99, that’s fair, but I’ve seen similar products that come as a three-pack for a few bucks more. If you have multiple AC units, you might want to grab two or three. Don’t be caught off guard when you open the package and see one sheet.
Real-World Test: A Month of Boondocking
I took the rig out for two weeks in late July. No hookups, solar only, the AC running off the inverter battery bank during the hottest hours. Dusty dirt roads getting in, wildfire smoke drifting through from a fire a hundred miles away. That’s the worst-case scenario for an air filter.
When I got home, I pulled the filter and it was gray-ish with a visible layer of dust on the surface. The coil underneath? Clean. Not spotless — there was a thin film that I wiped off with a damp cloth — but nothing that required foam cleaner or a coil comb.
That’s the test that matters. The filter did its job. Kept the expensive part clean. Cost me thirteen bucks.
I’m also running a Rellytech 11500 BTU Mini Split AC/Heating System in the bedroom of my rig, and I cut a piece of this foam to fit its intake as a pre-filter. Same result — the fine mesh behind it stays clean for weeks instead of days.
Do You Need This or Not?
Let me be straightforward:
Buy this if:
- You have a rooftop AC unit and hate paying OEM prices
- You need filters for multiple units and want one size that works for all
- You’re okay with cutting the foam yourself (it’s not hard)
- You want a washable filter that lasts more than one season
Skip it if:
- You expect a drop-in replacement with zero effort
- Your unit takes a filter larger than 16 x 40
- You have a warranty that requires OEM parts
That’s it. That’s the whole review. No marketing fluff, no ‘game-changing’ nonsense. It’s a piece of foam that filters air. It does the job. It costs less than the alternatives. The end.
If you pick one up through the links here, I might get a small cut — doesn’t cost you extra and it helps keep the lights on.
I’m going to order another sheet right now, actually. At this price, I’d rather have a spare in the cabinet than find myself at a campground with a dirty filter and no way to clean it. The foam’s cheap, the AC isn’t.