Custom product were well built and a much more useful than the locally available product. if not for the convector being an odd size these would be perfect. It is a true axion of measure 3 times before sawing. I was 1/8th too large. I was lucky that with a little force these do work/
For my furnace, the the corners of the filter weren't as strong as I would have liked, such that I had to "deform" the filter to get it to fit after the corners "crinkled." Other than that, they seem to be good. Time will tell.