What we say: Reduce friction, increase speed!

What they say:

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 a 13-tooth upper pulley wheel and a 19-tooth lower pulley wheel to provide absolute optimization of the rear derailleur
• 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 (long cage) nor with the clutch equipped Ultegra RD RX800/RX805
• CeramicSpeed products with coated bearings include a 6-year warranty.
• • Largest Cog:32
  • Fits Brand:Shimano
  • Fits Model:Ultegra R8000-SS , Ultegra R8050-SS/GS , Dura-Ace R9100 , Dura-Ace R9150
  • Drivetrain Speeds:11
  • Defined Color:Black