Making AC filters yourself?

Excellent replies - thanks for the information and valuable insight and experience shared here!

The edges of the foam filter on my Dometic suck upward and become useless. I want to figure out how to build a nice looking boxed frame around the bottom of AC return opening (for more filter area) and cover it with polyester media. Craig

The foam window unit stuff is cheap and easy to cut. When it gets dirty discard and put in another

That's how I buy the stuff, as long as the filter is just foam (not the Penguin or Carrier filters). I sell (full retail) a large enough piece to get several filters out of for $3.29.
You have to be cautious about using better material, unless you redesign the return to use a larger filter. Usually, better filters will restrict the air flow too much (it's a compromise given the tiny area available for filtering).

In a big box store, look for room air conditioner filter material.

Done it many times. Buy large pieces of the foam and cut to fit.

Ive been using the foam filters for a few years. I want to find something that flows a little better but still filters. I thought about the pleated filters but dont have the room to make it fit good. What about the old cheap blue fiber filters?

Wallyworld or most any big box store will have foam filters for window A/C's, just use scissors to trim to size. :)

I found foam replacement A/C filter material at Walmart in the weather stripping section of the hardware department. Cut to fit and I got two filters from each piece. I think the cost was about $5.

Yes!
I first tried to cut a 20*20 home A/C filter that looked like a green plastic door mat. Too thick. I now use the thinner fiberglass-looking filters. Can replace both of those long strips in our Coleman (non-ducted) unit twice out of one 20*20 filter.

I found some at a True Value hardware store that I used a pair of scissors to cut to size using the old one as a patter,
Don