3.5 oz CO2 tanks can be used in a wide variety of applications fitted to rifles and pistols so they can get many more shots per fill, better consistency and lower cost of operation. Fitted with high quality seals and ultra-reliable on/off valve. Tank weighs 17 oz full. Aluminum vessel with brass valve. On/Off Valve is Made in China, vessel made in USA and assembled with The Best 90 durometer Mil Spec orings. 3.5oz vessels do not require normally mandated DOT Hydro-testing because they are under 2" diameter, making them exempt. This is the famous Hangy Tank that can be used on Tau/BRNO, S&W, 78, MKI and the LD pistol. Too many applications to list.