Continental bicycle tubes are constructed of durable, seamless butyl rubber and are 100% inspected to ensure high quality and reliability. Seamless, and vulcanized to ensure uniform roundness and improved reliability at the valve stem. Every tube passes a stringent 100% quality control inspection. For 29" mtb rims, 29 x 1.75-2.5" Presta and Schrader valves have removable cores.