Tank Valve / 1st Stage regulator combo
The standard Brownie's Egressor packages are built with a tank valve / 1st stage combo. Combining the valve and 1st stage offers a lowed profile that the 2 components attached together.
The tank valve component screws into any standard scuba cylinder while the 1st stage component fits a standard 1st stage hose.
A feature to this combo is that it allows one to refill their small pony bottle several times off of a larger scuba cylinder while the pressure remains greater in the larger bottle.
One end of this fill adapter* screws into the valve/ 1st stage combo, the other end tightens down onto the larger tanks standard K valve. Open both valves and the air flows from the larger bottle to the Egressor pony bottle.
*Fill adapter sold separator*