This is a high quality plastic quick disconnect made by CM Becker for your 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. It's 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. This has been coined with the term "Lube and Turn".