A bicycle inner tube is usually made of butyl rubber. Butyl is a very elastic and at the same time airtight synthetic rubber. As with tyres, however, other additives are necessary for the rubber compound. The rubber compound used can result in significant differences in quality. Schwalbe inner tubes are extremely airtight and elastic. Thanks to their high elasticity, an inner tube covers a wide range of different tyre sizes. A distinction is made between mould-heated and autoclave-heated inner tubes. Vulcanisation in a mould results in more uniform wall thicknesses and therefore lower weights and significantly better air retention. This is why autoclave-heated hoses, which are easier to manufacture, have become increasingly rare in recent years. Schwalbe inner tubes have always been manufactured as mould-heated tubes. Each tube also has a valve, which is connected to the tube by vulcanisation.