So I've learned that "nominal size" is up for debate.So the filters I purchased are 16x25x4 just like what I needed, however, the product I received is much thinner in thickness than the name brand option. These filters are actually a full 1" thinner.The good news is that the width and height does cover my filter bay opening. I just am wondering how effective the thinner filter will be to reach the 13 rating.That was the other thing that I thought was interesting. When I received my filters, the label stated they were 8's. I immediately called to report this because I ordered 13's. I was reassured that if the check mark on the side was listed as 13"s then there were in fact what I ordered.I'm just not convinced that these are in fact 13's especially with the fact that the filter is a full 1" thinner.
I was disappointed with this purchase. The filter cardboard frames are very thin, and they are supposed to be the same size as we have always used, however they are enough too large that they do not slide in the frame easy. We had to practically jam them in the frame.