Inner tubes are generally made of butyl, a nearly airtight, flexible and robust rubber. There are also lighter and even more flexible tubes made of latex, but they require regular re-pumping and a puncture can only be repaired to a limited extent with a repair kit. The tube size is usually specified by the manufacturers as a range by the ETRTO specifications. The inner tube should be selected so that the tyre diameter and width are within the specified range of the inner tube. When choosing the valve, we recommend that you use the previous valve as a guide. This is because the car valve (AV) and Dunlop valve (DV) require a larger valve hole in the rim than the Sklaverand valve (SV).