It is simply a superior, nicely machined, brass push-on chuck, Presta fitting. Not quick release. The button just visible on the RH side allows you to release pressure in the chuck before you remove it from the valve, thus avoiding the explosive rush of air normally experienced. The adapter on the left screws onto a Schrader valve, to enable the use of the chuck. I have replaced the plastic chucks on my track pumps with these and they work beautifully.