Features BRASS MATERIAL: This CO2 refill adapter is made of brass, which is resistant to corrosion and wear, and has strong durability under continuous use. EASY TO INSTALL: With standard thread size, easy to screw on an empty CO2 gas cylinder, and not easy to fall off when using, rust and wear resistant. MAIN PURPOSE: Enables you to fill CO2 from larger bulk cylinders into smaller cylinders for convenient use, easy to operate, greatly improve work efficiency. STANDARD SIZE: The cylinder adapter can be used for large CO2 tanks with CGA320 connector, which has standard size and strong compatibility. WITH GASKET RINGS: Equipped with 4 large gasket rings and 5 small gasket rings, has good sealing performance, no air leakage when connecting the cylinder. Specification: Item Type: CO2 Refill Adapter Material: Brass Specification: TR21 4 to CGA320 Package List: 1 x Refill Adapter  4 x Large Gasket Rings 5 x Small Gasket Rings Package List 1 x Refill Adapter 4 x Large Gasket Rings 5 x Small Gasket Rings