It's a jug cap ...
you people make me laff! Brvheart has the right idea!
... I had to show a way of how the rest of the air-hosing is connected to the cap in order for it to pressurize and top off correctly, because as you can see some hoses go all the way down and some just past the cap. It Wouldn't hurt to put all of them all the way down but every time you top off it would make a bubbling noise
