CeramicSpeed 3D Printed Ti OSPW 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, titanium pulley wheels with Grade 3 Silicon Nitride balls Titanium pulley wheels are 3D-printed and hollow for additional weight savings and durability 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 Only compatible with Dura Ace 9100/9150 and Ultegra 8000-SS/8050-SS Not compatible with Ultegra 8000-GS or 8050-GS (medium cage) nor with the clutch equipped Ultegra RD RX800/RX805 Specifications: Compatibility: Ultegra R8000-SS , Ultegra R8050-SS/GS , Dura-Ace R9100 , Dura-Ace R9150 Speeds: 11 Speed Max Cog: 32T Color: Black/Silver