M.O.C. : M.S. CRCA with Powder Coted/SS 304. Prefilter Stage I : HDPE,Washable Eff. 90% down to 15-20 Micron Particle Size. Prefilter Stage II : HDPE,Washable eff. 95% down to 5 Micron Particle Size. Post Filters : HEPA Filtration Eff. 99.99% down to 0.3 micron particle size. Exhaust - HEPA(High Eff. Particulate Air) Sizes Available : 3' X 2', 4' X 2' , 6' X 2'