Gray, gas in quick disconnect with barb for gas line.Barb is 1/4". 1/4" or 5/16" beverage tubing is recommended for gas line. Tip N' Trick: Sometimes ball lock fittings are a challenge to quick disconnect "on and off" a cornelius keg. We recommend spraying the body connect on the keg first with a sanitizer solution which acts as a lubricant. When applying the ball lock fitting to the body connect, give a twist and turn to make it easier to connect. We've coined this term "Lube and Turn".