the 3M™ 750x series reusable half mask is a bayonet style dual filter design that fits a wide range of lightweight filters; the 750x line of small reusable masks features a valve with a soft sealing surface to ensure comfort and a unique head harness with an optional trigger strap; soft seal surface and low breathing resistance ensure comfortable wear even during long-term use; when used with the correct 3M bayonet filter, it can protect against risks associated with gases, fumes, or and particles; it can be connected to all 3M™ filters series 2000, 5000 and 6000 Sizes: 7501-S, 7502-M, 7503-L