Speedmaster Tube 20X1.5/2.3 AV

20 Inch Inner Tube. 

A bicycle tube is a rubber inflatable tube that is an essential component of a bicycle's tire system. It fits inside the tire and is responsible for holding the air that gives the tire its shape and allows it to roll smoothly over surfaces. Bicycle tubes are typically made from a combination of rubber compounds that offer flexibility, durability, and airtightness.