1.0mm Locking Nut
This 1.0mm locking nut is required on certain bikes with unusual derailleur hanger setups. Predominately used on OPEN (U.P, U.P.P.E.R, WI.DE) and Santa Cruz bikes but with other occasional manufacturers also. See the last page of these instructions for how it can be used. The design uses a 2.5mm Allen key to tighten so it can be attached or removed using a standard pocket multi-tool. If you’re unsure, please email [email protected] with details of your frame for advice.