Light design, 12T only 12.8g, 14T only 14g. Size: 50 50mm (12T)/57 57mm(14T). Weight: About 12.8g (12T)/ 14g (14T). 1 x Rear Derailleur Pulley. Si3N4 ceramic bearings Design,When rotating, the centrifugal effect of the outer ring can be reduced by 40%, and the service life is greatly extended.