The Box Three Rear Derailleur simplifies the features found on the Prime 9 Box One and Two rear derailleurs making for a fully featured wallet friendly rear derailleur. Including a Limited Slip Clutch, Sealed bearing pulleys and a solid construction Box Three Rear derailleurs are compatible with 11-46 and 11-50t derailleurs making it one of the most versatile derailleur offerings for Prime 9. IMPORTANT NOTES Prime 9 Technology™ View Prime 9 Drivetrain Compatibility Manual How is the Ebike variant different? View Prime 9 Comparison Chart View Prime 9 E-Bike Comparison Chart Why Prime 9?