Gas Mask - Monster Mask - Straight Tube - LrgNot for beginners, this gas mask delights those looking for a massive hit. The acrylic, straight tube water pipe fits into the mask and when worn creates an air tight seal. It is recommended to keep your eyes shut while using the mask. Fill the bong with enough water to submerge the end of the downstem, anything above that is personal preference. The choke is located at the back of the bong to help regulate air flow.