3/8 in (9.52 mm) brass socket quick coupler x 3/8 in FNPT, 4200 psi. Used anywhere high pressure connections are frequently assembled and disassembled and are ideal for quick exchange of spray nozzles and spray guns. Knurling on the socket sleeve allows for easy use. The ball lock design insures a solid connection every time. These quick couplers connect to all of the most common pressure washer equipment in the industry (cold water only).