This is the Lock Ring and O-ring kit to hold the front chainring and/or spider onto the motor drive pinion on the Bosch Gen 4 Drive Unit (BDU4XX)
Substantially tougher than the plastic nuts, although be careful not to cross thread the nut on the drive unit assembly.
PLEASE NOTE: If you have a Bosch Classic +, Active Plus or Performance system (Featuring a small sprocket on the front), you will require a different lockring.
We also sell the Bosch Spider Tool to safely remove and replace this nut. Available from our store.
Just to confirm it's to fit the following motor shape. If you require a Classic+ lock ring, you can find it on the dedicated Bosch Classic Lock Ring page.
Order and arrived fast
Accept no substitute, the kit is perfect. It comes in two pieces, both are needed for peace of mind.
One of the very few places that sells the lockring and O Ring together. Good price and delivered quickly.
For Bosch emtb gen 4 chainring - always fit the O ring, stops the chainring working loose