Box Box Rear Derailleur
What the checker says47will not fit
Run variant by variant through the e-MTB builder’s own engine. Every sentence below is the checker’s, unedited. Nothing here says this part fits your bike; it says what it does and does not fit among the parts we hold.
Checked against 442 verified e-MTB parts in this catalog. 336 produced no finding of any kind. Each variant produces 37 distinct errors and 0 distinct warnings.
Will not fit
- Will not fiterror · CassetteSpeed mismatch: Derailleur 9s, Cassette 12s. Shifter, derailleur and cassette must be the same speed count. On 30 of the 58 verified cassettes in this catalog. Applies to all 3 variants.
- Will not fiterror · ShifterSpeed mismatch: Shifter 12s, Derailleur 9s. Shifter, derailleur and cassette must be the same speed count. On 28 of the 53 verified shifters in this catalog. Applies to all 3 variants.
- Will not fiterror · ShifterDrivetrain mismatch: Shifter = shimano-12, Derailleur = box-prime-9. Shifter, derailleur and cassette must be one system. On 19 of the 53 verified shifters in this catalog. Applies to all 3 variants.
- Will not fiterror · CassetteDrivetrain mismatch: Derailleur = box-prime-9, Cassette = shimano-linkglide. Shifter, derailleur and cassette must be one system. On 16 of the 58 verified cassettes in this catalog. Applies to all 3 variants.
- Will not fiterror · CassetteDrivetrain mismatch: Derailleur = box-prime-9, Cassette = shimano-12. Shifter, derailleur and cassette must be one system. On 14 of the 58 verified cassettes in this catalog. Applies to all 3 variants.
- Will not fiterror · CassetteCassette too big: 52T cassette exceeds the Box Box One Prime 9 X-Wide max of 50T. On 13 of the 58 verified cassettes in this catalog. Applies to 1 of 3 variants.
- Will not fiterror · CassetteCassette too big: 52T cassette exceeds the Box Box Three Prime 9 X-Wide max of 50T. On 13 of the 58 verified cassettes in this catalog. Applies to 1 of 3 variants.
- Will not fiterror · CassetteCassette too big: 52T cassette exceeds the Box Box Two Prime 9 X-Wide max of 50T. On 13 of the 58 verified cassettes in this catalog. Applies to 1 of 3 variants.
Emtb drivetrain system, Shifter. 11 more findings from the same check, on up to 11 of the 53 verified shifters each.
Emtb actuation, Shifter. 9 more findings from the same check, on up to 1 of the 53 verified shifters each.
Emtb drivetrain system, Cassette. 8 more findings from the same check, on up to 9 of the 58 verified cassettes each.
Emtb drivetrain speeds, Cassette. 4 more findings from the same check, on up to 11 of the 58 verified cassettes each.
Emtb drivetrain speeds, Shifter. 4 more findings from the same check, on up to 10 of the 53 verified shifters each.
Emtb cassette capacity, Cassette. 3 more findings from the same check, on up to 9 of the 58 verified cassettes each.
Open a variant in the builder to see the ones that apply to your own parts.
$83.99 to $165.74 MSRP·290 g
What the maker states
- System
- Drivetrain system Box Prime 9 (9-speed)
- Speeds
- 9-speed (rear index count the maker rates it for)
- Actuation
- Mechanical (cable)
- Maximum cog
- Largest cog 50 teeth
- Mount
- Standard hanger
3 verified variants
| Variant | Price (MSRP) | Weight | Source | Last checked | Build |
|---|---|---|---|---|---|
| Box Three Prime 9 X-Wide (2019) | $83.99 | 290 g | maker’s page | 2026-07-14 | Build with this |
| Box One Prime 9 X-Wide (2019) | $165.74 | 290 g | maker’s page | 2026-07-14 | Build with this |
| Box Two Prime 9 X-Wide | $120.69 | not stated | maker’s page | 2026-07-31 | Build with this |
The rest of what the maker states2 not published
2 further fields the checker looks for are not published by Box, so we leave them blank rather than estimate them, and those 2 checks stay silent on this rear derailleur. They are maximum cog top and total capacity. Each is recorded as “not stated by the maker (not checked)”.
Source: each variant links the maker’s own page in the table above. Last checked 2026-07-14 to 2026-07-31.
Checked against
The checker ran this model against every verified part below that it has a slot for, the same way it checks a build in the builder. What follows is the verdict it actually produced for that specific pairing — not a recommendation, and not a guarantee any of these parts fits your own bike.
- 9point8 Fall Line 30.9 / 125mm (INLINE) (Dropper Post) No conflicts found
- BikeYoke Divine 2.0 Dropper Post 31.6 / 125mm (Dropper Post) No conflicts found
- BikeYoke Divine SL Dropper Post 30.9 / 80mm (Dropper Post) No conflicts found
- BikeYoke Divine SL Rascal Dropper Post 30.9 / 80mm (Dropper Post) No conflicts found
- BikeYoke Revive 3.0 Dropper Post 30.9 / 125mm (Dropper Post) No conflicts found
- BikeYoke Revive Max 3.0 (34.9) Silver Ltd. Dropper Post 34.9 / 125mm (Dropper Post) No conflicts found
6 of 227 counterparts with a page of their own that the checker actually probed this model against, in alphabetical order by brand and model — never by price, popularity or the verdict itself.