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.

There’s tons of great party games — but unlike the rest, Box ONE is designed to challenge just ONE person: YOU! And you alone. The clutch wasn’t able to stop the chain from skipping down the cassette when freewheeling. Alex EvansReducing 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. General operation was quiet, too, and shifting under power was good – as long as the shift lever was pushed far and hard enough. However, it states its system isn’t compatible with 12-speed chainrings or non-narrow-wide offerings.

The 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. 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. 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 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. 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 XTR

Box Components Box One Prime 9 drivetrain compared to SRAM NX Eagle, SRAM GX Eagle and Shimano SLX, XT and XTR

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. The cassette uses Shimano’s Hyper Glide (HG) freehub body which is different to SRAM’s XD Driver and Shimano’s Micro Spline system.

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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. Performance-wise, GX Eagle is significantly better with crisper shifts, a lighter shifter actuation and a wider-ranging – and lighter – cassette.