Chainring lockring tools from Park Tool. Integrated 3/8" drive fitting allows compatibility with most ratchet handles and torque wrenches for tightening to proper torque specifications Heat-treated and plated 4140 steel construction ensures durability and long life Fits lockrings with 50 mm outside diameter and 8 notches Replacement for Bosch 0275009003 tool Removes and installs the front chainring lockrings found on DJI Avinox & Bosch Gen 2 e-bike motors once the crank arm is removed