Box Four Prime 9 Derailleur (Black) (8 Speed) (Wide Cage) (Clutch)

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While everyone else keeps adding more and more gears, the Box Four Prime 9 Groupset takes a different approach. The engineers at Box decided that sometimes simple is better so they developed a groupset with a wide ratio range over only 8 cogs. The benefit is that fewer gears reduce the chain angle on the low end; making the chainline more direct across the whole range; improving component longevity and power transfer. The rear derailleur boasts a limited-slip clutch with instant engagement and constant torque which prevents dropped chains and minimizes chain slap.


  • Prime 9 Technology for less derailleur travel and better chainline, less wear, and improved lifespan
  • Box's "8 speeds is enough" derailleur
  • Limited Slip Clutch 
  • Stamped front/rear cage 
  • Direct channel cable stay
  • Bearing pulleys
  • Not compatible with Shimano direct mount derailleur hangers (requires traditional derailleur hanger)

Speed: 8 Speed
Shifter Compatibility: Box Prime 9 (8 Speed)
Shift Mechanism: Cable Actuated
Max. Tooth: 42T
Min. Tooth: 11T
Chain Wrap Capacity: 31T
Cage Material: Aluminum
Chain Retention: Clutch
Color: Black
Weight: 328g

This product was added to our catalog on November 6, 2020

Box Prime 9 Model Comparison