A steamroller (also called zoom tube) is a term used by smokers of cannabis to describe a type of pipe that consists of a hollow tube with both ends open, and a bowl on one side near one end. It is presumably called this because of its resemblance to the front wheel of the piece of machinery. Another common explanation for the name comes from the fact that once the chamber is full of smoke, and the user removes their back hand to facillitate inhalation, the smoke, or "steam", appears to "roll" over itself as it is sucked from the chamber.