If you're home draft system is a mix of ball lock kegs and commercial sanke kegs, having a coupler with ball lock adapters is a huge plus. This allows you to have all your draft lines ending in a ball lock quick disconnect, making it quick and easy to swap lines from sanke keg to ball lock.
Note that the gas-in adapter has a small line cut into the body of the adapter where the bev-out adapter is smooth.
The check valves will need to be installed before first use. The silicone check valve is inserted on the side gas-in port and the check ball and ball retainer are inserted on the top bev-out port.