Both Shimano and aftermarket Center Lock front hubs were designed for 20mm oversize thru-axle use. The large interface caused Shimano to use an internal diameter notched system for the Center Lock disc rotor lockring. Unlike other Center Lock rotor lockrings that are compatible with existing Shimano tools, the original 20mm axle version SM-RT80 rotor lockring (used on the Saint mountain group) requires a special tool. This is that tool, the TL-LR20 Center Lock Lockring Tool. It is designed solely for this purpose, but the sizeable chunk of machined steel also makes a great workorder or benchtop paper weight when not being used for it's intended purpose.

The thin wall, 12-spline tool fits perfectly in the oversized lockring, and has a 1/2" socket interface for extra leverage and proper installation to 40Nm via a torque wrench, but also 15/16" standard wrench interface that is open or box-end friendly and works just fine with a decent size adjustable wrench as well. You may not use the TL-LR20 Center Lock Lockring Tool often, but if you need it, you really do, as there is no other version we are aware of. Serious mountain bike shops use it regularly, and if you have a bike with Saint and a 20mm thru-axle front Center Lock hub with the internally notched rotor lockring, you really need to have this tool on hand at home. Tip: if you bring your bike into your LBS for service, you may want to have the LR20 with you, as many shops either won't have it, or won't be able to find it. Later models moved to the external, OD notch design (SM-HB20 for 15/20mm thru-axle).