22-M-MALE X 3/8"-FEMALE NIPPLES - Brass pressure washer screw nipple. Screw nipples are used in combination with pressure washer screw couplings anywhere high-pressure connections are frequently assembled and disassembled. They connect to all common 1/4 inch (6.35 mm) or 3/8 inch (9.53 mm) pressure washer equipment in the industry and converts M22 metric thread size to standard National Pipe Thread (NPT) size.