Besides 3M, there seems to be 2 major sellers of filters on here. The other brand I received had no label as to what the MERV rating was but stated online to be 2. These filters are noticeably thicker, fluffer, holding up to a bright light did not let as much light through and without formal testing, look like they will do a much better job at MERV 11 than the other brand at MERV 12 with no markings. Plus these are stamped as 11. I returned the other brand and purchased these. Very happy with my desicison!