The new design of Backplate, a laminate to avoid stress points and now fitted with a ball race which replaces the original Oilite bearing.
M5 Back Plate Assembly with Bearing
If you have an original M4 Starter then you need the M4 Legacy plate. The original M4 Main Pulley is a fractionally smaller diameter and thus the pulley centres are marginally different, and the belt would be too slack using an M5 backplate. Please send us an email to support your order if you need one of these.