Continental Hermetic Plus Bike Tubes Tour 28 - 700x 32-47c Inner Tubes with 40mm Auto / Schrader Valve (Pack of 2 Tubes) - For worry free cycling, we recommend the Hermetic Plus tube. Its improved formula is lighter and more compact, which renders it very puncture resistant in the presence of higher butyl amounts and greater wall thickness. Since it retains air longer, it's a favourite among bicycle rental agencies - 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.