The Shimano TL-LR21 is required for mounting and dismounting 9-45 cassettes with external teeth on the lockring for the MICRO SPLINE freehub body standard.
Features - Shimano TL-LR21
Hardened steel for rigidity and durability
Usage
For installation and removal 12-speed cassettes with 9-45 teeth on the Micro-Spline freehub