Introducing the RS Pro M20 size Stover nut, a hexagon all-metal self-locking nut. The self-lock function is produced by having irregularly shaped threads at the top of the nut, these threads grip the corresponding bolt threads, giving a stronger hold. Stover nuts are resistant to shocks and vibration. They do not require any form of anti-vibration washer. With a bright zinc plated finish, they provide resistance to corrosion and are made from grade 8 steel for durability and environmental resistance over a long period of use.