Keg coupler is a key component of the draft beer system that connects beer and gas lines to the keg. Couplers are not universal as they need to fit the specific keg valve they are made for. A, D, G, M, S and U systems are the major keg systems used across the world.
This coupler is designed for A system keg valves which works with notable German beers and hence is more commonly known as German slider style keg coupler.
Branding is the reason behind this multiple keg coupler-valve systems. A keg system has come to be associated with a specific brewery and differentiated from others when kegs went for refilling.