Ultegra FC-R8100 chainrings are constructed with high quality aluminum and are compatible with FC-R8100 and FC-8100-P 2x 12-speed cranksets.Features-Aluminum with anodized finish and carbon fiber reinforced plastic for extreme durability and light weight-Hollowglide technology provides high rigidity and cuts down on weight while maintaining strength-Offers better power transfer and quicker, more precise front shifting-52t outer chainring is for use with 36t inner chainring-Asymmetric 110 BCD-Compatible with HG 12-speed chainsItem Specifications-Ring Position/Type:Outer-Tooth Count:52-Drivetrain Speeds:12-Chainring BCD:110 Asymmetric-Material:Aluminum w/ Carbon Wrap-Color:Black-Defined Color:Black