A keg coupler is what connects the keg to the air line and beer line. It’s what physically “taps” the keg valve, causing gas to flow in and beer to flow out. Couplers can differ from keg to keg depending on the type and brand of beer being purchased. Many breweries adopt a valve style for all of their beers, so if you should decide which coupler to purchase based on which brewery you buy beer from most often. The type of coupler should match the type of keg valve.
The coupler types and keg valves are differentiated by letters: A, D, G, S, and U. “A” couplers are typically used in German keg valves. “D” couplers are most often used with American, or Sankey, keg valves. “G” couplers fit ale keg valves, most notably those from Boddingtons, Anchor, and Fuller’s. “S” couplers fit many European keg valves. “U” couplers are a match for Guiness and Harp keg valves. Purchase one or all keg couplers to start enjoying draft beer at home.