BEWARE
I ordered 16x25x4 filters. Mind you every other brand of filters (3M, BestAir, Filtrete, Honeywell, even generics) of the same advertised dimensions fits perfectly. I bought a six pack when I installed my last other brand filter so I would have them ready when needed. They did arrive promptly. At the next change, I discovered that they were way too small. I emailed customer service and got a snotty, condescending email about how I should have checked the nominal size. A standard is a standard for a reason. This is a scam and I would warn buyers to BEWARE.