Abstract: A gas tank valve and yoke for mounting gas passaging structure on the valve in which a gas tank valve stem and yoke set screw are both adapted to be engaged by a single wrench. The same wrench turns the valve stem to open and close the gas tank valve, and turns the set screw into secure engagement with the gas tank valve to hold the yoke in a fixed, self-retaining position on the valve. A torque rod is connected to the outer end portion of the set screw for conjoint rotational movement with the set screw about the longitudinal axis of the set screw for turning the set screw. Pin and hole arrangements on the yoke and valve body are provided to discriminate against using an undesired gas or gas passaging structure.