1.Hex head, female threaded inside, metal material, anti-loose hex nut. 2.Used with a machine or cap screw for mechanically joining materials together. 3.Used widely for matching screws or bolts. Package Contents: 300(+/-2%)Pcs x Nylon Lock Nuts Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.