HPC 1/4" MPT stainless steel quick connect socket: the socket half of a 1/4" quick connect, with a 1/4" male pipe thread (MPT) end.
Stainless steel quick connects last much longer than brass, especially when you are running bleach. This socket is used most often on your high pressure gun, for connecting 1/4" nozzles, a JROD, wands and oth