This black vinyl protective cap for scuba cylinder valve outlets will fit all standard 200 bar DIN scuba cylinder valves, including DIN valves containing a DIN-to-Yoke insert and all 200 bar DIN valves sold by Dive Gear Express. The cap helps to keep debris out of scuba valves when not in use. Many dive operations use this type cover as a visual indication the cylinder is FULL (cap on) or EMPTY (cap off). It includes a small length of black nylon string to help attach it to your tank.