BOX shook up the drivetrain market with the release of their wide range 9-speed drivetrains. The prime 9 derailleurs are built for 11-50t cassettes without all the headaches of adjusting 12 gears. The Box One Prime 9 rear derailleur is Box's top of the range Prime 9 offering with all the bells and whistles. It features an adjustable clutch, precision sealed bearing pulleys and a fully forged construction.

Who's this item for: Anyone already running a Box Prime 9 speed drivetrain or those looking to upgrade to Box's innovative wide-range 9-speed offering.

Number of gears: This is a 9-speed derailleur

Weight: 290g

Materials: This derailleur is made from hardened alloy steel, stainless steel and nylon composite with a hard onyx finish

Chain and cassette compatibility: This derailleur is designed to pair up with the rest of the Box One Prime 9 drivetrain components. However, it will also perform well with any other Box Prime 9 components.

Max cassette range:

• Minimum sprocket size: 11T
• Maximum sprocket size: 50T
• Total capacity: 39T

Clutch style: This derailleur uses Box's Tri-pack limited-slip clutch, the clutch is adjustable on this model.

Cage length: This derailleur has a forged inner and outer long cage for durability and to accommodate a wide range cassette.

Pros: Fully forged construction, sealed bearing jockey wheels and a fully adjustable clutch.

Cons: Not as friendly on the wallet as BOX's Two/Three Prime 9 derailleurs but you do get what you pay for.