Tier1 Replacement for Electro Air 16x21x5 Merv 11 Air Filter 2 Pack Upgraded media rated at MERV 11 to capture 90% of particles, 1-3 microns in size Replacement for: White-Rodgers FR1000-100 Filter can also be used as a replacement filter for White-Rodgers electric air cleaner series SST10/SST1000 collection cell A811-0398/F811-0398 (Power must be disconnected when using a filter in place of a collection cell) This product is listed and rated by Underwriters Laboratories as U.L. Class 2