This is a high quality plastic quick disconnect made by CM Becker for your beverage line.
Barb is 1/4". 3/16" beverage tubing is recommended.
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".