Once the Deluxe Fitting and Hose Kit quick disconnect fittings are permanently mounted to the head of the booster, the fittings are of course exposed when the hoses are not connected. Best practice is to protect them from contamination. You can cover the fittings with a clean plastic bag, or you can use this plug and cap set. The pair is essentially a set of quick disconnect male and female fittings with 1/4 NPT plugs installed hand tight.

Important: These are not intended to be pressurized. Always install and remove both the plug and the cap at the same time because if either is inadvertently pressurized it will be difficult to remove due to check valves in the booster and hoses that can make it impossible to bleed the pressure. If that happens, to bleed the pressure then cover with a towel and use a wrench to remove the 1/4 NPT plug on the end.