Nylon inserts to prevent nut from loosening. Ideal for high vibration applications. Zinc plated for corrosion resistance. Contains sizes: M4 x 0.7mm, M5 x 0.8mm, M6 x 1.00mm, M8 x 1.25, M10 x 1.500mm & M12 x 1.75mm. Plastic divider storage case.