Abstract: A valve assembly for dispensing a gas, particularly for medical use into a connector of a gas using device, comprising: an outer body with an internal passageway containing a valve seat and a valve member which is lifted from said seat by rearward pressure, an inner body threaded into the passageway of the outer body and having an internal passage and a plunger within said passage which includes an activating member adopted to hold the valve member away from the valve seat when the plunger is moved rearwardly, the plunger and inner body having interlocking parts by which rotation of the plunger requires rotation of the inner body, said inner body has a stepped profile on the outside for mating with a complementary stepped bore in the outer body and a stepped bore on the inside for mating with a hose connector.