The K-Lok adaptors/quick disconnects are compatible with Andale (Snaplok), Lancer Pacific (Fatlock) and other brands of draft beer quick lock fittings that are often seen in commercial pubs and bars.
 
 
This fitting is typically used on the end of the liquid line that attaches to the keg couplers and has a check valve built in. This check valve prevents liquid from draining out of your beer line when it's disconnected (what's known as a dry break).
 
The most common fitting to put on the thread of the back of this fitting is the duotight 8mm female to 5/8" BSP female fitting.  Alternatively you can use the hex nut, barbtail and a 5/8" seal and then use a hose clamp.
 
These check valves are designed to fit liquid lines which would then typically fit into your keg coupler. They are made with 5/8" BSP male threads. Depending on what size of gas line you are using you can choose from multiple different hex nut and barbs or our push in fittings to go on the back of these.