Praher Plastics 050-000 1/2" Single Union Ball Valve SKT x SKT. Praher’s unique spanner wrench handle provides for easy valve seat servicing - just pull handle off ball stem & use as a tool. Praher’s unique threaded true single union ball valve design provides for: user friendly handle operation - union nut load does not transfer onto ball seat, thereby providing user with easy handle operation even if valve not operated for a long period of time. “Below grade - blocked seat flooded suction design” - valve seat will not blow out from static pressure if union nut removed.