Continental Race 28" 700x25-32c Bicycle Inner Tubes -42mm Long Presta Valve (Pack of 4 w/ Conti Sticker)Continental bike tubes are constructed of durable butyl rubber and are 100 percent inspected to ensure quality. The tubes are seamless and vulcanized for uniform roundness and improved reliability. Material: Butyl tubes with renowned Continental quality Durability: Each and every inner tube passes a stringent 100% quality control inspection Design: Seamless construction, with a mold-cured vulcanization, to ensure uniform roundness and give a smooth ride and handling.