Reducing tension on the adjustable clutch did lighten upshifting but increased the amount of chain slap and reduced overall chain stability, making the adjustment to a lighter setting a compromise not worth making. Although the derailleur’s limit screws and b-tension were easy to set, indexing the gears was much harder than I was expecting. Cable tension was very sensitive and there was an incredibly small sweet spot where the gears shifted well. However, general shifting was good and with a positive push of the lever (more on this below) the derailleur didn’t miss any shifts and wasn’t hesitant in its operation. It also happily shifted gears under power.

The maximum jump between gears is eight teeth (consistently between the lowest three gears), with the jumps decreasing as the gears become higher. The consistency of the gaps makes adjusting cadence to a gear change more gradual. Box Components Box One Prime 9 drivetrain compared to SRAM NX Eagle, SRAM GX Eagle and Shimano SLX, XT and XTRThe factory setting for the derailleur’s clutch is stiff, which means its initial movement has a significant resistance peak before the cage is able to smoothly pivot forwards. General operation was quiet, too, and shifting under power was good – as long as the shift lever was pushed far and hard enough. Compared to Shimano, pricing for Box One Prime 9’s derailleur and shifter sits in a middle ground between XT and XTR, while the cassette price is similar to Shimano’s SLX-level.

From a pricing perspective, Box Components Box One Prime 9 drivetrain is comparable to SRAM’s GX Eagle level (once you’ve removed the cranks and chainring from the GX groupset). Performance-wise, GX Eagle is significantly better with crisper shifts, a lighter shifter actuation and a wider-ranging – and lighter – cassette. Enjoy the thrill of challenging situations with our range of survival games. Whether you like to go solo or work in a team, our selection is full of hair-raising games like Fortnite for Xbox One, Halo Infinite and Remnant: From the Ashes. And when it comes to first-person shooters, how about grabbing a copy of the latest Call of Duty Modern Warfare 3. With new guns, maps and an all-new Zombies mode, you’ll be in for a jaw-dropping experience. Shifts are stiff and vague-feeling, while the cable-pull lever has too much travel. The balance between chain control and shift performance isn’t quite right either. Installation was relatively straightforward and I was particularly thankful for the shifter’s hinged bar clamp, which meant I didn’t need to remove the grips or brake lever from the bar to install it.The lever has a lot of travel before a shift is engaged, too, so a fair amount of sustained force was required to change each gear, which didn’t feel particularly natural. To access the fourth shift I needed to move my thumb more than was possible without rotating my wrist around the bar. It also required a lot of sustained strength. Because the derailleur’s cable stop is positioned vertically (similar to Shimano) a large loop of cable is required to avoid a sharp bend that could reduce shifting performance.

The Box One Prime 9 drivetrain might last longer than SRAM’s offerings – thanks to the chunkier chain and cassette – but I don’t think you’d be able to live with the high-resistance shifter lever once you’ve experienced a lighter system. The clutch wasn’t able to stop the chain from skipping down the cassette when freewheeling. Alex Evans Its top shell and cable pull lever are made from cast aluminium and the machined bar clamp is hinged to make installation or removal easier. I-Spec II and Matchmaker adaptors are also available. The clutch interferes with the derailleur’s ability to easily move into lower gears because of the mechanical coupling between the shifter and derailleur via the gear cable, leading to heavy shifter paddle operation. Box Components provides installation and set up guide videos on its YouTube channel to help with the finer details of getting the drivetrain installed and running smoothly. I followed the instructions to the letter to give the drivetrain the best chance possible of performing as intended.The cassette uses Shimano’s Hyper Glide (HG) freehub body which is different to SRAM’s XD Driver and Shimano’s Micro Spline system. The chain, made from hardened alloy steel, has chamfered shifting edges to increase shifting performance, and solid plates and pins to make it stronger. The finish on the chain and cassette have shown little signs of wear during the test period and the teeth haven’t become hooked or the chain links stretched. The cable port is vertically positioned. Alex Evans Box Components Box One Prime 9 drivetrain details

Compatible with HG Freehub Bodies. Compatible with Standard Derailleur Hangers (Non Direct-Mount). Compatible with most 10,11, & 12-speed wide / narrow chain rings. Prime 9 chain must be used. The cable release lever was also quite stiff but felt way more positive. It was only possible to shift one gear at a time, though. My test sample wasn’t supplied with an I-Spec or Matchmaker adaptor, although these are available. Alex Evans I didn’t find myself stretching lower gears out with increased cadences on flatter sections or grinding up steeper hills in higher gears for longer because the gear ratios were too far apart. Compared to SLX M7100 (1,221g), XT M8100 (1,153g), XTR M9100 (996g), and GX Eagle (1,163g) it is significantly heavier.Weight-wise, the full 1,375g Box One Prime 9 setup I’ve reviewed is roughly equivalent to SRAM NX Eagle’s 1,362g weight and Shimano Deore M6100’s 1,330g. When lower gears were selected and chain length grew, the derailleur’s clutch tension caused the cage to be stiff pivoting forwards, so the cable-pull shifter lever was heavy throughout the lever’s throw. However, it states its system isn’t compatible with 12-speed chainrings or non-narrow-wide offerings. The cable-pull lever can shift four gears at once if pushed far enough, but accessing the last shift is virtually impossible while riding because of the amount of travel required to engage the gear.