Scope of delivery: 4 x M25 ER20A clamping nuts. Model: ER20 A, material: 40CR steel and black oxide finish. Precision ground and hardened. Feature: After precision grinding and hardening, the hex nut can be a great replacement for the broken part and can fit most tool holders. Suitable for: Hex nut can work with ER type handle, bore cutter, tool bar, extension bar nut and other tools.