The Bosch Lockring Tool do Lockring Assembly Active/Performance. The tool is used to loosen and tighten the locking ring in the chainring mounting.  Bosch Lockring Tool do Lockring Assembly Active/Performance Features   The Bosch Locking tool for Active and Performance Line ebike, is used to loosen and tighten the locking ring in the chainring mounting. Original Bosch tool in workshop quality and therefore 100% accurately. For the professional repair this Locking-Tool is required