This tailpiece is a replacement for the gas-in barb that comes mounted on our D1505 Sanke Tap. It will not work as a 5/16" beer line connection due to the lip on the back side of the fitting.
Tailpieces are fittings which connect beer and gas tubing to the different parts of a draft system. One side of the tailpiece features a barb to connect the tubing to, and the other side is held against the tap or faucet shank with collar nut.
Tailpieces are available in a range of barb sizes to fit up to your tubing size.