Check the listing for details. AX-Lightness Wheel Ceramic Bearing Set - HSC Ceramics. Condition: New. Listed at 163.65 USD. AX-Lightness Road Ultra Wheel Ceramic Bearing Set I've been competing in Triathlon for 6 years and I immediately noticed the difference that the ceramic upgrades from HSC made to the movement of my drivetrain. With all the hard work I put into my training it's great to know that my bike components are moving fast and freely to keep me at the top of my game. – Owain Matthews Triathlete and Triathlon Coach, Australia About the brand HSC Ceramics is proudly Australian owned. Product Features: 3-5 times longer lifetime than steel bearings; 5-9 watts energy saving with the wheel ceramic bearing upgrade; ABEC 7 standard alloy steel bearing races - less friction and durable; Grade 3 Si3N4 ceramic balls - super smooth; C 3 clearance - less vibration and smoother riding; Light touch rubber seals - energy saving; Designed for Cycling Use; Bearings: 2 x 6801(12x21x5mm), 3 x 6803(17x26x5mm),1 x 6903(17x30x7mm); How to check the bearing size: Please open your current hub by removing the End Cups to see the bearings. On the bearing rubber seals, you should be able to see the bearing code such as "6803 2RS". If you can't find the bearing code, you can measure the bearing's Inner Diameter (ID) x Outer Diameter (OD) and match the measurements with our bearing size listed. With the ID and OD, you can identify the bearing without removing the bearing out from the hub. For instance, a 6803 bearing size is ID 17mm x OD 26mm x W 5mm; Please feel free to let us know if you have any questions.