CeramicSpeed cartridge bearings are an upgrade option for any cycling discipline. These bearings provide extremely low friction, improved power transfer, and a service life that far exceeds traditional steel bearings.Grade 3 Silicon Nitride balls. Hardened steel races. Reinforced polymide cage and non-contact seal to keep dirt and moisture out. High resistance to poor lubrication. Can be used for any cycling discipline. Sold as each. Hand built in Denmark. Item Specifications: Bearing I.D. (mm), 12, Bearing O.D. (mm), 21, Manufacturer Number, 61801 (6801), Material, Ceramic, Thickness, 5,.
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