These nuts feature a nylon insert on their upper face. The internal diameter of the insert is a little less than the diameter of the nut’s thread. When tightened the insert grips onto the thread of the bolt. The grip of the nylon insert resists turning forces thus preventing the nut from coming loose when subject to vibration. In many cases a nylon locking nut is preferred to using a split washer with a standard nut. This useful box of nuts contains an assortment of common metric sizes. There are 6 sizes, ranging from M3 to M10; the box contains on average 195 pieces. The nuts are steel with CR3 zinc plating to prevent corrosion, made to DIN 985 standard. Supplied in a handy plastic organiser box 210 x 110 x 30mm.