Box Three Prime 9 X-Wide Rear Derailleur Black - boxcomponents

Box Three Prime 9 X-Wide Rear Derailleur

$83.99 Sale Save
2 reviews
Size X-Wide Cage
Color Black

Only 0 left in stock


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.

Our Best All-Rounder Derailleur
For Light/Medium Terrain
Limited Slip Clutch™
Bearing Pulleys

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: Die Cast / Aluminum
• P-Knuckle: Injection Molded / Glass-Nylon Composite
• Linkages: Die Cast / Aluminum
• Cage: Stamped / Aluminum
Finish: Matte Onyx
Speeds: 9
• Platform
• Ebike
• Non-Ebike
• Shifter
• Box One Prime 9
• Box Two Prime 9
• Box Three Prime 9
• Derailleur Hanger: Non-Direct Mount
Weight: 290g/10.2oz

Q: Are Box Prime 9 derailleurs compatible with Shimano "direct mount" hangers?
A: No, Shimano direct mount hangers are proprietary and are not compatible with Box derailleurs.

Q: Is the Box Three Prime 9 Derailleur compatible with other 9 speed components?
A: No, traditional 9 speed systems use a Cable Pull that is not compatible with Prime 9.

Q: Are Box Prime 9 derailleurs compatible with drop bar (road) shifters?
A: 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.

Q: How should I clean my Box Three Prime 9 derailleur?
A: 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.

Q: How do I make adjustments to the derailleur?
Please see our installation video at

Q: Can I adjust the Limited Slip Clutch on my derailleur?
A: No, the clutch system on this derailleur is not adjustable.


Standard Mount vs. Direct Mount Derailleur Hangers

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.

Customer Reviews
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United States United States

Good for Less Aggresive Riding

I bought the Box Three derailleur for a budget bike build. After three months of regular XC riding, the clutch came loose rendering the clutch useless and the shifting unusable until the derailleur cage was put back on. The cage screw had a lack of Loctite. Luckily, I discovered this before I hit the trail. I am a XC rider and after shifting under load and hard shifting in general, the limit screws got pushed out of a nylon insert holding the screws in. I contacted Box customer support and they resolved the issue quickly. Their customer service is excellent. I would recommend this for beginning or novice riders. For hard riding XC/trail/enduro guys, I recommend Box One/Two derailleurs.

Canada Canada

Excellent Replacement for a Stock Derailleur

This is my replacement for a stock Shimano Altus because I desired an 11-50T cassette. After correcting my derailleur hanger angle with the proper alignment tool (it wouldn’t be fair otherwise), this derailleur shifts crisp and fast. I discovered that I do not need a derailleur hanger extender. There is good clearance on the 50T sprocket.