Drag Specialties Heavy Duty Premium Inner Tubes For Harley Drag Specialties Heavy Duty Premium Inner Tubes are a dependable tube and are offered in a variety of sizes with either center or side metal valve. Drag Premium Tubes are the brand's top-tier inner tube offering. Specifications: Drag's most premium, thickest inner tube for Harley Tr-4 straight / metal 8mm valve stem Center or offset valve location (depending on model) Features: Tubes feature a full 2 mm thickness compared to a standard tube 1.2 mm thickness 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 Sold individually