with high quality Spindle Interface Type: , Hollowgram SI/SL/Compact For Bike Type: Time Trial Triathalon, Cruiser, Cyclocross Bike, Dirt Jumper, Folding Bike, Mountain Bike, Recumbent Bike, Road Bike - , Road Bike - Touring, Bike, Track Bike, Tricycle, Unicycle, Urban Bike - Fixed Gear. Oil-free -lubricating, ceramic ball with oil-free -lubricating properties, so ceramic cannot grease Insulation, rolling body with ceramic ball, you can achieve the between the inner and outer ring insulation High speed, the use of ceramic ball speed than the general speed is much higher , bearings in the water and high temperature environment, the oil is easy to wash or kill, so that the bearings bad, the use of ceramic balls as a rolling body, do not worry about these problems. Waterproof: bearings used in the water, grease washed off, the bearings broken, the use of ceramic balls, you can normally use in the water. Surface Roughness:Ra 0.05 Model Number:Ceramic Ball colour:Silver + black Material:Rubber + ceramic Diameter: Inner: .30mm Outer: .42mm Thickness: .7mm Package Contents: 2 * 6806 Ceramics Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.