The regulator first stage attaches to this valve using a yoke fitting, and there is a sealing O-ring that is held in the face of the valve outlet where it mates with the regulator. The difference between a DIN regulator first stage and a yoke regulator first stage is the manner in which the regulator attaches to the tank.
A DIN regulator screws into a tank valve, and a yoke regulator fits over the top of tank a valve and clamps onto it with a tightening screw. The DIN system is by far superior, but a diver may find it preferable to use a yoke regulator depending upon his style of diving and tanks. The DIN to yoke adapter on the yoke bottle still allows the diver to round his regulators to and from it. Yoke regulators use a more-or-less flat tank valve that has an O-ring pressed into a small grove on the flat side of the valve. A Yoke adapter for DIN in your dive gear to allow you to use both the same day without having to switch out regulator sets. DIN valves can handle higher pressures than yoke valves, and are used on high pressure tanks. DIN regulators can be designed to withstand higher pressures than yoke regulators. Is it safe to use a yoke adapter valve insert and yoke regulator on the scuba cylinders? Yes, it's okay to adapt outlet scuba valves for use with all modern Yoke regulators but older yoke regulators with the yoke assembly marked (or unmarked).
Scuba Gear Technical Information:
Pony bottle connector for YOKE.
0.4 liter cylinder international type connector.