I always use Filter Buy cause its a real pain to find my sizes. So I always buy 4 at a time so I know I do not need to run out and pull my hair trying to find my size. So when I put the last one in, I order 4 more. So convenient.
I have an old electric "filter" in my furnace. During some service work the tech recommended I replace with a better air filter. The size is a bit odd, 22x25x4 but this standard size seems to be working fine.
I like your design of one piece cardboard structure, others I have purchased were two sections paper taped together. I noticed that it looks like there is a lack of pleats compared to all the filters I have used.