Note: At times I will need to source other companies to provide these to you. Don't be alarmed if it looks a little different than the QDs that are in the photos and are a different brand.
Stainless steel quick disconnects(QD) are designed for higher pressure than us car guys will be using but will hold up much better to corrosion than zinc or brass. Also, it looks much better and really doesn't cost much more.
You really don't need this part. The MTM Foam Cannon comes with a zinc plated/brass plug, but I prefer stainless.
Inlet = 1/4" Male Plug for (Quick Disconnect) QD: This 1/4" male plug inserts into a female QD coupler.
Outlet = 1/4" (National Pipe Thread) NPT Male: This 1/4" male threaded end screws into a female 1/4" connection.
Mosmatic 20" Lance Outlet -> 1/4" Male QD Coupler -> 1/4" Male Plug -> MTM Foam Cannon Inlet