Proven time and again in World Cup race conditions, the ZERO Ceramic bearings are the ultimate race day weapon. Oversized Grade 3 balls roll on races which are ground to a mirror finish after receiving Magnetite and then Cryogenic treatments for hardness and longevity. More durable and with even lower rolling resistance than any 2RS bearings, they come closer to that magic "zero" rolling resistance number. Enduro Bearings uses Silicone seals which are more slippery than rubber seals used by other ceramic bearing suppliers. We get more email and blog feedback on the ZERO's than any other bearing, describing the noticed difference in downhill rolling speed. They also win the independent wattage output tests when stacked against the competition. Features: All measurements are in millimeters ABEC 5 precision cartridge bearing CERBEC USA Grade 3 Si3n4 Silicon Nitride balls 52100 high carbon Chromium alloy races Races receive 3 cryogenic treatments and a rust proof Magnetite finish "VV" type 2-lip non-contact Silicone labyrinth seals Specifications: Bearing I.D. (mm): 15 mm Bearing O.D. (mm): 24 mm Manufacturer Number: 6802 Material: Ceramic Thickness: 5 mm