Made from Butyl Rubber, Schwalbe tubes are well known for their extremely high air retention and elasticity. Schwalbe tubes undergo a vulcanization process which ensures constant wall thickness and high air pressure retention. All tubes are inflated and stored for 24 hours to test the air pressure retention. Afterwards, each tube undergoes a careful visual inspection. Only a good quality tube can cover very many tire sizes which aren&';t possible if the tube isn&';t highly elastic in nature. For example, tube no 17 can fit tire widths between 28mm and 47mm. Airtightness - Apart from the quality of the ingredients, the purity of the rubber mixture is crucial to the quality of the tube. The base material is therefore sieved at enormous pressure through seven filters before being extruded. All tubes are inserted into a mould and inflated for vulcanization to ensure constant wall thickness and high air pressure retention. Reliability - All tubes are inflated and stored for 24 hours in order to test for air pressure retention. Afterwards each, individual tube undergoes a careful visual inspection. This special quality control helps prevent unpleasant surprises and is why, over many years, Schwalbe tubes have become highly respected for outstanding reliability by bicycle dealers. Group tube system - Only high elasticity and good quality allows a tube to cover very many tire sizes. Tube No. 17 can fit tire widths between 28 mm and 45 mm and that is a big advantage to the trade and simultaneously it vouches for the tube&';s quality. Only an extremely high-quality and reliable tube is up to to this requirement. Valve - All valves are nickel-plated and threaded and valve inserts are replaceable. Also, Schwalbe tubes with the classic bicycle valve are capable of pressure testing thanks to a high-pressure valve seal. And it is plain to see as each tube is crowned with a transparent polycarbonate dust cap. Specs ETRTO - 18-622 > 28-622, 22-630 > 25-630 Size French - 700 x 18C >700 x 28C Valve Type/Length - Presta/60mm Weight - 105g