The Roller Boys Ceramic will make your bike ride so smooth that you will never stop anymore. The composite material is strong and durable and the special teeth pattern makes sure you can shift to a higher gear with the speed of light. The ceramic bearings make sure your pulleys will roll super smooth. High-quality pulley wheels are a must-have for every serious bike rider, with the Roller Boys Ceramic you are good to go.High-end ceramic derailleur pulleys:- High-end and super easy-to-install ceramic pulleys with special tooth patterns for super quick and smooth shifting gears.Features:- 11x13T Ceramic derailleur pulleys- Ceramic bearing for minimal resistance and exceptional durability- Composite material provided by EMS Swiss, with 40% glass-fiber mixture- Sealed bearings with aluminium cover for optimal durability- Lubricated with special ceramic light oil for extra smoothness- Compatible with 11-speed Shimano GRX (810/815)Specifications:- Pulley size: 11/13T- Bearings material: Ceramic- Gears: 11-speed- Compatible with brands: Shimano- Part materials: Grivory EMS- Weight (g): 26