D and S series, 303 Stainless steel, beer coupler check ball retainer.
Beer should flow out of the keg to the faucet. However, you do not want beer to flow backward back into the keg. You also don’t want all the beer in your system to spill out on the floor when you uncouple a keg.
There is a check ball (or other device in other couplers) that is small enough for beer to go around in order to get to the faucet. The same check ball keeps beer from flowing backwards into the keg or on the floor.
This is the retainer that keeps that check ball from flowing up into your beer line.
Don’t hesitate to contact us if you have any questions about this or any other part we carry. We want to help you get your order right the first time and to keep your project underway.