PSEI0428E John Guest 3/4 in CTS ProLock Coupling ProLock Push-to-Connect Couplers are the easiest and most dependable way to join Copper, PEX, or CPVC pipe in any combination with no solder, glue, or tools required. JG ProLock fittings use a collet with stainless steel teeth that grips the pipe when fully inserted, and an EPDM O-Ring to provide a permanent, leak-proof seal. When twisted into place, the locking cap locks the pipe in place and creates an audible click, ensuring maximum security. Disconnection is just as easy with no tools needed; simply twist the cap 1/4 in. turns counterclockwise to unlock then depress collet against the fitting to remove the pipe.