The filters I normally buy fit the opening exactly. These filters are about 1/2" too small all around so I have to use duct tape to prevent air from being sucked in around the sides. I would rather pay a little more and get filters that fit exact.
Just put filter in furnace last week. It's hard to rate something this early. It seems to fit well. I will look at it in a month and see what it looks like.
I purchased these for a condo furnace - they are too long but easily cut to fit the furnace. Worked well last year, and I replace annually so as soon as furnace is cleaned, we will insert a filter. Highly recommend.