Drag Specialties Inner Tubes With Rubber Valve Stems Drag Specialties Heavy Duty Inner Tubes are a dependable tube and are offered in a variety of sizes with either center rubber or side rubber valve. Features: Butyl rubber Centered valves stems are for wheels with the stem hole drilled in the center of the rim Side valve stems are for wheels with the valve hole drilled off-center Valve stem is 8mm stem diameter unless otherwise noted 8mm is the most common hole size drilled into modern wheels .625 (15.875mm) stem diameter (Tr-15) tubes are for some older bikes including some pre-1980 Harley Davidsons