Pressure washer screw coupler and screw nipple set. Pressure washer screw couplings and screw nipples are used in combination anywhere high-pressure connections are frequently assembled and disassembled. They connect to all common 3/8 in pressure washer equipment in the industry and convert M22 metric thread size to standard national pipe thread size for leak-free connections. Screw couplings and screw nipples are easily hand tightened and are ideal for connecting hoses together.