Stanley J7515 Proto 1/2-inch Drive 3 Piece Locking Impact Extension Set Solid one-piece design helps prevent the locking components from becoming loose or disengaged. Patented locking feature locks sockets to the extension with exceptional force. Knurled shank provides a slip-resistant grip when hand-turning the extension. Proto 1/2" Drive 3 Piece Locking Impact Extension Set Includes the following items: J7503, J7505, J7510.