Guinness® and Harp Lager use a coupler that is very specific to their brand. The Taprite CH5300U U System Keg Tap Coupler is a coupler that is compatible with European "U" system kegs. To tap a keg all you have to do is pull out and then down on the lever handle to properly couple the keg.
A high-capacity pressure relief valve has been incorporated as an integral part of the coupler body. This serves two purposes: First, when functioning with other relief devices in the system, it will prevent a key from reaching pressure in excess of recommended working pressure. Secondly, it allows the user to relieve pressure when needing to prevent or correct dispensing problems.