Description Improve comfort and breathing pattern using The Metal Wrench by Responsive Respiratory. It is a small metal wrench ensures satisfaction and offer excellent value. The Oxygen Metal €˜E' Wrench is an adjustment stem on all CGA 870 standard post valves for 'D' and 'E' sized medical oxygen cylinders. Features a slot for easy removal of oxygen tank seals. Available with optional Heavy-Duty Chain to connect to regulator. Stamped with on/off arrows.