The DiversiTech QT-2 line piercing tool features a valve core in the 1/4 in. male port. Simply pierce the line and back seat the needle. The flow starts when the depressor type charging hose is connected. The flow shuts off automatically when hose is removed. If the valve core is not desired it may be removed. Connect hose, pierce line, and back seat needle. Valve core can be removed or changed at any time without loss of refrigerant if needle is front seated.