The 37mm Air Sampling Cassette w/”PTFE” Filters are designed to meet all NIOSH, OSHA, and EPA requirement for air sampling standards. All 37mm cassette housings are manufactured in house and are available in both two and three piece configurations. All 37mm cassettes are individually assembled and preloaded under stringent quality assurance standards with only the finest quality membrane and support pads. With support (Zefluor). 2.0µm pore, 2 piece housing.