The Michelin Airstop Tube is a .9mm thick butyl tube designed for increased puncture resistance..9mm thick butyl tube for increased puncture resistanceItem SpecificationsWeight194gValvePrestaISO Diameter559 / 26" mtnISO Width40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,33,34,35,36,37,38,39mmLabeled Size26 x 1.6-2.1"Valve LengthShort 32-40mmTube CompoundButylValve CoreFixedValve ShaftSmooth