[M8×1.25 iron  & unichrome 11pcs]

[M4×0.75 iron  & unichrome 20pcs]

[M6×1.0 Iron  & trivalent chromate 18pcs]

[M4×0.75 Iron  & trivalent chromate 20pcs]

Use in places where the bolts are prone to loosening. The metal friction ring touches the screw threads of the bolt, creating a function that increases the torque of the screw to create a loosening effect. Heat resistant, vibration points, and reusable.