Shimano SLX FC-M7120-1 Boost Crank

The Shimano SLX FC-M7120-1 Boost Crank sits in Shimano's SLX groupset — the upper tier of their trail-capable MTB lineup, sitting just below XT and XTR. Designed for single-chainring drivetrains, it pairs with 12-speed SLX systems and brings Shimano's proven engineering to riders who want reliable, capable performance on technical terrain without stepping up to the top of the range. Three arm lengths — 165mm, 170mm, and 175mm — let you match the crank to your fit and riding style.

The FC-M7120-1 is built around Shimano's Hollowtech II crank arm construction, which routes the spindle through the drive-side arm to reduce weight while maintaining stiffness under load. The Boost chainline — 52mm — is engineered to work with Boost-spaced frames, keeping chain alignment tight across the cassette and supporting the wider rear hub spacing that's now standard across most modern trail and enduro geometry. The crank is designed to run a direct-mount chainring, giving you a clean, rattle-free interface and the flexibility to swap ring sizes as your trails demand.

Shimano SLX FC-M7120-1 Boost Crank Specs at a Glance

• Groupset: Shimano SLX M7100 series, 12-speed
• Chainring compatibility: Single direct-mount (1x only)
• Boost chainline: 52mm
• Crank arm construction: Hollowtech II
• Available arm lengths: 165mm, 170mm, 175mm
• Bottom bracket interface: Shimano Hollowtech II (24mm spindle)
• Color: Black
• Intended use: Trail, enduro, all-mountain MTB

Design Benefits

1. Boost-optimized chainline for modern frames: The 52mm Boost chainline is designed to work seamlessly with Boost-spaced frames — the geometry standard found across the vast majority of current trail and enduro bikes. This keeps chain angles consistent and reduces wear across the full range of your 12-speed cassette.
2. Direct-mount chainring interface: Rather than using a spider, the FC-M7120-1 accepts a direct-mount ring that sits flush against the crank arm. This eliminates flex points and keeps the drivetrain quieter and more precise on rough descents where a spider-mounted setup might rattle or flex under hard pedaling.
3. Fit-tuned arm length options: Crank arm length affects both biomechanical efficiency and ground clearance on technical lines. With 165mm, 170mm, and 175mm options available, you can dial in the setup that matches your inseam, riding style, and the type of terrain you spend most of your time on — whether that's flowy singletrack or aggressive chunk.