Ocean Pro Tank Valve Protector
Keep one of these protector's on the top of your tank valve to keep the sand and dirt off your o-ring. It is also used as the universal sign of a full tank - cap on - full, cap off - needs filling. Intended for use with Yoke valves. While it can also be used with DIN valves, for these a screw in DIN valve protector would be a better choice.