Tires are ring-shaped parts, either pneumatic or solid (including rubber, metals and plastic composites), that fit around wheels to protect them and enhance their function. Pneumatic tires are used on many types of vehicles, such as bicycles, motorcycles, cars, trucks, earthmovers, and aircraft. Tires enable better vehicle performance by providing traction and load support. Inner tube-almost all tires, many motorcycle tires, and many tires for large vehicles such as buses, heavy trucks and tractors are designed for use with inner tubes. Inner tubes are torus-shaped balloons made from an impermeable material, such as soft, elastic synthetic rubber, to prevent air leakage. The inner tubes are inserted into the tire and inflated to retain air pressure. An inner tube is the tube inside a protective outer tire that is generally used to hold air and keep the entire tire inflated to a proper level. Inner tubes are very fragile in many cases and therefore need some sort of outer protection in order not to become easily punctured. If one inner tube does become damaged, it may be possible to repair the inner tube with an inexpensive patch. Not all tires have an inner tube, because they are able to hold air with other components. Most passenger car tires fall into this category. However, there are vehicles on the road, such as motorcycles and heavy trucks and tractors that may have inner tubes, though there may be other options for these types of vehicles as well. When most people think of an inner tube, its application on a bicycle may be the first thing that comes to mind.