C4 Gas Mask. Surpasses NATO and related Triptych protection requirements for face, eyes and respiratory tract protection against chemical and biological warfare agents when used with an approved filter / canister. Compact and lightweight. Unique stretchy fabric head harness with six point attachment for excellent fit. Adjustable with two pull straps. Easy in-field maintenance. Equipped with drinking system adaptable to both US M1 and Canadian canteen caps. Optional configuration for First Responders, where head harness is directly attached to face piece.