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 Compatible with Dura Ace 9200 and Ultegra 8100 series (Fits 11-30 and 11-34 Shimano 12spd Cassette options) Specifications: Compatibility: Shimano Dura Ace 9200, Ultegra 8100 Speeds: 12 Speed Max Cog: 34T Color: Black/Silver