Use this Duotight fitting to connect gas lines to keg couplers or in long - draw beverage systems (20 - 25 ft long). It's great for homebrewers and professionals in the beverage industry. The fitting has a 9.5 mm (3/8 in.) side and a 5/8 in. FPT side, and it uses EPDM double O - rings. It can handle up to 100 psi of pressure, making it a reliable choice for your kegging operations.