Michelin AirComp UL 650 18-23C 60mm Valve – 2018 The Michelin Aircomp Ultra Light Tube is a butyl tube optimized for competition.Material Lightweight Butyl Size 650X 18-23C Valve Type 60mm Presta Valve Wheel Size 650C/29″. Posted in Bicycle Parts, Bicycle Tubes, Cycling, Outdoor Recreation, Sporting Goods