1.Nylon-insert lock nut, polymer-insert lock nut, or elastic stop nut, is a kind of locknut.
2.It is a nut with a nylon insert that resists turning.
3.The plastic insert is placed at the end of the nut, and its inner diameter (ID) is slightly smaller than the diameter of the screw.
4.The inserts elastically over the threads of the screw, but threads are not cut into the nylon.

Specification:
Material: 201 Stainless Steel
Thread Size: M4
Pitch: 0.7mm
Hex Width: 7mm / 0.28"
Height: 5mm / 0.2"
Package Content: 10 x Hex Lock Nuts