These quick connects are similar to the low pressure hose BCD fitting on SCUBA regulators, except they are rated to a whopping 350bar.  Handy for quick swapping of fittings on your gas mixing equipment for your supply bottle with different valves, or for quickly changing between yoke and DIN.  They are supplied clean for oxygen service.  Please note that the descriptions are of the actual adaptor, so the one in the far left of the picture is female QC to male NPT.

Specifications:

• Material: brass

• Thread: ¼” NPT

• Pressure rating: 300bar

• O ring: Viton

Note that unlike BCD quick connects, these don’t seal when you disconnect (and can’t be disconnected under pressure) – this helps to avoid potential impingement sites in oxygen service.  The shutoff sort exists, but is much more expensive and hardly justified for SCUBA systems.