Moscow Mule Mugs, Solid Copper 16 Oz Set of 2 Bar Mug

Dude - It's LIQUID PROPANE GASyou screw it on, open the valve, and TURN THE TANK UPSIDE DOWN.the liquid flows into the little tank, the gas flows out of the little tank, and the little tank fills up with LIQUID PROPANE which turns into a gas when it flows out