Silicone O-Rings for airsoft green gas pistol/rifle magazines that prevent cold spitting gas from touching your hand and reduce wasted gas. All you have to do is place a ring on top of the valve and press it in with the end of a green gas can or propane adapter. They measure 3mm in diameter and work on almost any fill valve. 10x Count Compatibility: -Pistol Magazines -Rifle Magazines -Gas Grenades -Grenade Launcher Shells -Gas Shotgun Shells -Any Standard Airsoft Gas Fill-Valve (Note: If using a high-pressure gas, such as red gas, black gas, or propane, the o-rings may blow off if not secured.)