Box One Prime 9 Rear Derailleur - boxcomponents
Box One Prime 9 Rear Derailleur - Box®

Box One Prime 9 X-Wide Rear Derailleur

$194.99 Sale Save
7 reviews
Size X-Wide Cage
Color Black

Only 0 left in stock


The Box One Prime 9 Rear Derailleur takes the advantages of our legacy 9-speed drive-train but adds the advancements of a modern 1 by; a fully adjustable Tri-Pack™ Clutch, and an x-wide cage optimized for an 11-50T cassette. Forged construction steps up the durability and performance to an unparalleled level. Suited for the most demanding terrain. 



      Our Best Performing Derailleur
      For Aggressive Terrain
      Adjustable Tri-Pack™ Limited Slip Clutch
      Precision Sealed Bearing Pulleys
      Pivot-Tech™ Cable Stay

      Box One Prime 9 11-50T and also 12-50T eBike Cassette Black
      Box Two Prime 9 11-50T and also 12-50T eBike Cassette Black
      Box Three Prime 9 11-50T and also 12-50T eBike Cassette Black
      Box One Prime 9 Chain 126L DLC Black
      Box Two Prime 9 126 Link Chain Nickel
      Box Three Prime 9 126 Link Chain Polished
      Box One Prime 9 Shifter Black
      Box Two Prime 9 Shifter Black
      Box Three Prime 9 Shifter Black

      · B-Knuckle: 3D Forged / Aluminum
      · P-Knuckle: Injection Molded / Carbon-Nylon Composite
      · Linkages: 3D Forged / Aluminum
      · Cage: Forged / Aluminum
      Finish: Gloss Hard Onyx
      Speeds: 9
      Cable: Box One Slick Coated
      · Platform
      · Ebike
      · Non-Ebike
      · Shifter
      · Box Two Prime 9
      · Box Three Prime 9
      · Derailleur Hanger: Non-Direct Mount
      Weight: 290g/10.2oz

      Prime 9 Box One & Two Installation

      Are Box Prime 9 derailleurs compatible with Shimano "direct mount" hangers?

      No, Shimano direct mount hangers are proprietary and are not compatible with Box derailleurs.

      Q: Can I install this on my bike that uses a b-link for my current derailleur?
      A: Yes! All you need to do is remove your old derailleur and the b-link leaving the standard hanger attached to your bike frame. You can now mount your Box Components derailleur directly to the hanger on your frame.

      Q: Can I install this on my bike that currently has a direct mount hanger?
      A: Possibly, you will need to see if your frame manufacturer or a third party like wheelsMFG offers a standard mount hanger for your frame.

      Standard Mount vs. Direct Mount Derailleur Hangers

      Is the Box One Prime 9 Derailleur compatible with other 9 speed components?

      No, traditional 9 speed systems use a Cable Pull that is not compatible with Prime 9.

      Are Box Prime 9 derailleurs compatible with drop bar (road) shifters?

      No, Box Prime 9 derailleurs are not currently compatible with drop bar shifters, but we do offer a clamp for our shifters to mount on some 31.8mm drop handle bars.

      How should I clean my Box One Prime 9 derailleur?

      We suggest removing the derailleur from the bike and using a soft bristle brush or rag with soapy water or a mild de-greaser. We do not recommend pressure washing, strong solvents or de-greasers as they could degrade the surface coating.

      How do I make adjustments to the derailleur?

      Please see our installation video at

      Customer Reviews
      4.4 Based on 7 Reviews
      5 ★
      4 ★
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      1 ★
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      Filter Reviews:
      Steady S.
      United States

      Love this thing

      Can’t get enough!!!! Keeps me on trail for more miles with less issues

      Alexander S.
      United States United States

      Better than the box 2

      I'd like to add the box 1 shifter before my judgment!

      Richard G.
      Czech Republic Czech Republic


      I am really happy with the Box One derailleur because it works so well! Fast and accurate, but must only work with cassette BOX two or one He doesn't understand much with cassette three and four. Cheers Gaspi

      Robert A.
      United States United States

      Tough & Reliable

      Excellent product

      Kevin G.
      United States United States

      Box 1 Prime 9 Perfect

      This thing will take a beating. Going on over a year with no issue