Box calls their new Prime 9 Tech a counter-intuitive approach, but when we think back… fewer gears meant lighter weights, less wear & less finicky shifting. So why was it that we keep embracing more gears in our cassettes these days?

Box Prime 9 speed MTB drivetrains – Nine is fine!

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!
count ’em. just nine cogs.

Sure, the reasons we have adopted 10, 11 & 12 (OK, even 13 a bit) drivetrains have not disappeared overnight – smaller steps in between gears for smother shifts, more optimal cadence due to those smaller steps, plus the ability to offer unprecedented cassette gearing spreads that allowed the adoption of many single chainring 1x setups. But mountain bike drivetrain disruptor Box thinks the simplicity, durability & performance of their new 9-speed groupsets outranks those small improvements, and in many cases still matches them.

Prime 9 conceptual details

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!

Simple. Dial 12 cog back to 9 and you get a more simple setup. And yuo will shift less. Box still offers 11-50 cassettes in 9-speed (close to the SRAM 10-50 benchmark.) And with 25% fewer cogs in that cassette, obviously you are going to save weight.

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!

Durable. Box’s Prime 9 still uses the modern standard 11-speed Shimano HG freehub, but has more tightly spaced cogs in the back. As chains got narrower the inner chain width decreased which actually increased chain strength, but the side plates got thinner too, making for a wash in overall chain durability. Instead, Box 9 keeps the latest 11/12-speed internal chain spacing (that means it works with any modern narrow/wide 11 or 12-speed chainring), but gets thicker plates for an overall 9-speed chain width. That’s strength improvement on both aspects, making a more durable chain. Plus, the narrower overall cassette width delivers straighter chain line for quieter running, longer drivetrain life span & faster shifts. Fewer gears (with the same spread) also means less shifting, so shifting components will last longer.

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!

Compatibility. Box 9 all-steel cassettes fit on the same Shimano 9/10/11 freehub, so nothing proprietary or hard to get ahold of (no XD, XD-R, or even MicroSpline). That means every wheel out there will work, but also that those steel cogs will last longer than alloy.All work with standard HG freehub bodies, but also are more tolerant to a mm or two outside of spec.

Prime 9 technical details

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!

Box’s Prime 9 drivetrain is available in 3 spec levels – box one (orange), box two (red) & box three (blue). Interestingly, the 2020 Box line also includes a 8-speed box four (yellow) drivetrain too. Each gets a 11-50 tooth spread in its cassette (the same as SRAM NX Eagle 1×12). They also all include a modern clutch to eliminate chain drops.

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!

Each Box Prime 9 group includes a two button 9-speed trigger shifter (bigger internal gears, fewer shifts, less wear & longer life); a new 9-speed rear derailleur with a clutch, less cage movement, more reliable chainline & lower wear & tear; a lighter wide range 9-speed cassette that fits on a regular Shimano hub, then the unique 9-speed chain.

What’s the catch?

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!

In reality, it looks like Box 9 is the near the top in all aspects. Sure, gearing steps are bigger than normal, but special shift pins mean smooth shifts when needed. And Box contends that mountains bikers don’t need such small cadence jumps, instead preferring consistent steps, as well as broad top & bottom gearing options. And while the cassette loses weight, the stronger 9-speed chain is heavier than a 12-speed chain.

To us that sounds like worth concessions, and for sure something worth giving a try. Plus, Box is typically a more-affordable alternative – from top-spec Box One down to entry performance spec Box Three.

Pricing & availability

2020 BOX ONE Prime 9 speed MTB, performance modern 9-speed 1x mountain bike drivetrain, Nine is fine!

Prime 9 groupsets and individual components are available for pre-order now direct from Box, with availability projected by the end of the year – December 2019. A complete Box One Prime 9 groupset with its light & carbon goodness will set you back $627. The alloy Box 2 is just $270, and a much easier sale to commit to. Then at $195 including shifter, derailleur, cassette & chain, Box Three is the lowest cost of  entry. Take it one stop lower to Box 4 and it is just $155, but with a smaller gearing range.

Maybe it’s time to upgrade your mountain bike drivetrain by dropping some gears….


  1. It seems to have taken forever to get back to this point. I always wondered why 12 speeds were needed to make a 11-48+ spread work.

    • Because you don’t want massive gaps between each ratio. With too-few cogs, each gap has to be larger, and you’re more likely to find yourself ‘lugging’ one ratio or spinning the next.

  2. > that means it works with any modern narrow/wide 11 or 12-speed chainring

    12-speed chainrings are not compatible between manufacturers.

  3. This is missing the point. The point of 11, 12 or even 13 cogs is so that there is less of a gap between gears and having a range that works with 1 chainring. This also shows the price premium for 11,12 speed. I admit, a 11, 12 speed cassette would probably cost more, but the shifter, derailleur and chain shouldn’t. That being said, $627 for a 9 spd group is ridiculous when compared to a Sram Eagle GX or Shimano XT 12 speed groups. .I would certainly take the weight penalty, if any, using 12 spd, over 9 spd

    • Pricing to weight is absurdity out of whack. Top tier cassette weighs and costs as much as XTR 12. It should be less given less cogs. Rest of the group set is just their e bike drivetrain, with multi shifting. But good luck with multi shifting, it still suffers from significant force needed to shift and significantly long distance to throw a shift.

  4. I’m tired of replacing chains and cassettes so often. If this offers a longer wearing option than I’m sold. I don’t really mind the bigger jumps between gears.

    • Literally a 12 speed NX cassette weighs and cost as much as the box 2 cassette. You could do 2 12 speed XT for the price of the “good” box 1 cassette. Not to mention all the options with 11 speed price/weight ratios. This drivetrain just doesn’t make sense. If you want cheap, go Microshift, if you want value go xt

    • If your running a 1×9 as opposed to a 1×11 or 1×12, how would this reduced wear? You still have the cogs that are spread across the same spacing, doesn’t matter if its 6, 7, 8, 9. 10, 11 or 12.spd The cross chaining would be the same.
      I applaud Box for competing against the big two, but think this 1×9 is obviously a step in the wrong direction

      • Atually the wear on a 1×9 will be bigger – lesser cogs mean that each of them will be working more. They also try to tell us that wider chain would not be stretched that much, but it will – the stretch is not in the link plates, but lies within those micro gaps between the plates and pins.

        And jump beyond 20% between the gears are felt really well, so i’d use these drivetrains in AM/Enduro, never in XC.

  5. Let the road bikes get more gears….when was the last time a wider spread between gear ratios really messed up your ride or caused a problem? you just change your cadence or effort to compensate. But when was the last time you cursed the ever changing# of gears and the resulting incompatibility, quick wearing components, etc? How many more gears are we going to add???? The most important thing we have achieved has been an overall wider range (big cogs like 50 and 52+ tooth cassettes) if we can do it with less cogs then I’m all for it…

    • Prime 9 chains have internal dimensions that are compatible with modern Wide / Narrow chainrings and perform similarly to 11 / 1 2 speed chains. Externally, Prime 9 chains have similar dimensions to existing 9 speed chains. This unique geometry allows for thicker side plates than 12 speed drivetrains which resists stretching over time increasing shifting performance while decreasing wear on the cassette and chainring

      Note: Other 9 speed chains are compatible with the Prime 9 derailleurs and cassettes but may increase the possibility for dropped chains, we recommend using a Box Prime 9 Chain for optimal performance!

  6. I’m skeptical that thicker plates would mean longer chain life. Wear (inaccurately called “stretch”) is to the pins and rollers. Which apparently aren’t wider with the Box 9 speed setup if I read correctly.

      • Wear happens at the inner plate pin hole’s beveled edge against the pin. Since the edge is heavily beveled, I do not believe the actual plate thickness is a contributor to wear rate.

    • Stretch is a fine word to encompass “chain elongation due to wear” as it is intuitive and doesn’t step on the toes of any other terms dealing with similar mechanical properties.

  7. I’m not seeing the value proposition for Box 2 at $270 vs. a UK sourced SLX 1×11 transmission set at about $280 shipped that also includes the crankset and bottom bracket.

  8. It’s not for me, but I know some guys who would dig this.
    For me, I use my arms to cycle, so I will stick with my 11-speed Di2 setup on both trikes (one 11×3 ‘road’ trike, and one 1×11 [with mid-drive e-assist] ‘off-road’ trike). Mechanical shifters are the devil for ‘handcycles’ due to the constant rotation with the ‘cables’ being attached to the pedals. Back when I still had them my shifter cables needed to be adjusted very frequently (depending how how many miles I was putting in as much as 2-3 times per month).

  9. I see some value here, since I still run a 2×9 setup and mostly use the granny ring as a bailout gear so a wide range 9 speed might be enough climbing gear to run a single ring, although I’d be willing to go 11-42 to reduce the gear steps.

  10. I see the benefits of simplicity here. Yes if the incline you’re climbing is consistent, like a fire road, having the better resolution of a 12 speed would be beneficial to keep your optimum cadence. But, how often does that happen? The trails I ride are so up and down that bigger steps between gears would actually be appreciated. How often are you grabbing multiple gears before a climb? Or clicking a whole bunch before a descent? I almost never just grab one gear. 12 speed almost becomes more of a pain.

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