21 1/2 x 23 1/2 x 1 HealthSmart AC, Furnace Filter with (1) BioSponge Plus Replacement Actual size: 21 1/2 x 23 1/2 x 3/4". This filter provides maximum protection against airborne contamination. Make your home Healthy. Provides maximum protection against airborne contamination. 60 Day Money-Back Guarantee. Includes: (1) permanent aluminum frame & (1) BioSponge Plus 1" thick filter. Simple to use. Fits all makes and models of furnaces and air conditioners. Maybe the last furnace filter you will ever purchase. All furnace filter frames are backed by a 10 year warranty!