Replacement stems for older Manabloc systems that originally had black stems. The older black stems with a smaller diamond pin are no longer manufactured. There was trouble with the black diamond pin breaking off so they redesigned the stem, changing them to red or blue color and increasing the size of the diamond pin to resist breaking. If your existing ManaBloc stems are black, red, or blue and turn 360 degrees this is the correct product for your system. Stem turns ¼ turn to off or on, but will turn 360 degrees around. This newer stem uses the red T-handle (50601) which has a larger diamond slot.