The PUREBURG 2-Pack Replacement HEPA Filters are compatible with Therapure models TPP440F, TPP540F, and TPP640F. These True HEPA filters have a life span of 6 months and come in a pack of two. The filters are designed to fit air purifiers and use Hepa-17 filter media. The dimensions of the filters are 17.8 x 5.25 x 2.4 inches.