CeramicSpeed Oversized Pulley Wheel System Description: The CeramicSpeed Oversized Pulley Wheel System provides optimization and increased efficiency of the rear derailleur through its extremely low-friction bearings and unique overall design. Features: Features 13-tooth upper and 19-tooth lower, aluminum pulley wheels with Grade 3 Silicon Nitride balls Robust cage crafted from polyamide and carbon fiber for durability and light weight Coated bearing races increase bearing service life by increasing hardness of race and reducing corrosion Compatible with Shimano GRX 810 & GRX 815, Shimano Ultegra RX 800 & Ultegra RX 805 Cassette compatibility up to 11-36 Four spring tension settings allow customized setup based on ride conditions Specifications: Compatibility: Shimano GRX 810, GRX 815, Ultegra RX 800, Ultegra RX 805 Speeds: 11 Speed Max Cog: 36T Color: Black