QRS = Quick Release System.
A great system for handling your lenses.
Change the adaptor on your AOI wideangle lens and place your macro lens into a bayonet system, and your lenses are ready for easy "snap-on" / "snap-off".
Your housing then needs the adaptor as well to receive the lenses. (and you might light a lens holder with the same mount, to place your lenses safely while it is not on the housing.
Works particularly well with Fantasea housings, Seafrogs TG6 housing and others. (will work with almost any housing that has an M67 thread on the port)