Protects your HVAC system and offers superior filtration performance to 1" filters. 20"x25" nominal size. Unpainted steel cabinet. Comes with 210 Clean Air Filter, which has more than 9 times the filtration area found in 1" filters. Guaranteed with our Pure Fit Promise: Self Seal� technology, interlocking rails, and Clean Coil Commitment. Easy to maintain - simply change the Air Purifier's filter once up to every 12 months. Versatile installation . compatible with systems located in basements, attics, closets, and more. Compatible with the 213 Healthy Home Filter, 213CBN Odor Reduction Filter, and 216 Allergy & Asthma Filter.