A tube is a hollow cylinder made of metal, plastic, glass, rubber, or other material that has open ends or perforated walls. It can also be described as an enclosed hollow cylinder through which liquids and/or gases can flow. Tubes are used for a variety of applications including plumbing, manufacturing, and transport. Most tubes are cylindrical, but they can also be bent or twisted into a variety of shapes. One of the most common uses for tubes is in electronics, where they are used to connect components in a circuit.