Seems like 2 different BVM valves are being discussed here....one is the Festo....the blue ones..H-QS-3 or 4 or 6mm....that are generally used for fuel tubing, or gas tubing check valves, not for retract hookups, which use the 1/16" I.D. tubing....

The part I was referring to is BVM #5758, the BVM Air Fill Valve which I believe is a Clippard Valve with a barb on one end that fits the airline tubing, and the other which has a standard auto/bicycle weird thread, something like a 5/16-34 ?....you can use a standard screw on or clamp on tire inflator on it, or the swivel screw cap that BVM sells that fits standard tire inflator hose...

You can also tap it 8/32 so that Spring Air filler will fit....the purchase is a little thin to tap for the larger Robart filler, which is close to 1/4" if I remember correctly....

The internals of the valve are displayed on Clippard's website....I forgot the catalog page number...It is internally spring-loaded with no rubber diaphragm and good for up to about 300PSI....BVM states a conservative 180 PSI continuous...

Tom