Shimano's direct-mount chainring lockrings use a specific 41mm, 16-notch interface that you can't service with a standard bottom bracket tool or cassette lockring tool. If you're working on XTR M9120, XT M8120, MT900, or other Shimano direct-mount cranksets, the Park Tool LRT-4 is the dedicated lockring tool for the job.

The LRT-4 is CNC-machined from 6061 aluminum, which serves two purposes. First, the machining holds tight tolerances so the 16 notches on the tool engage the lockring cleanly across the full face. Second, the aluminum construction is softer than steel, so it won't chew up the lockring surface the way a poorly fitting steel tool or pliers would. The face is machined flat to maximize contact area with the lockring, which distributes force evenly and prevents the tool from cocking to one side under torque.

The tool body has a 36mm hex fitting, so you can drive it with a 36mm open-end wrench or adjustable wrench for removal. For installation, though, you'll want to pair it with the Park Tool TWB-36 Crow Foot and a 3/8" drive torque wrench to hit the manufacturer's torque spec. The TWB-36 and torque wrench are sold separately. While you can get a lockring off with an adjustable wrench in a pinch, torquing it back on by feel risks either under-tightening the ring or damaging the interface.