A hex nut with a nylon filled collar at its back end. When a screw or bolt reaches the collar, the threads and nylon form a tight frictional fit, restricting movement between the nut and bolt or screw when subjected to vibration. The nylon insert comes in various colors.
Designed for use with like-material screws and bolts. They are able to be reused more times than a two-way reversible lock nut. Steel nylon insert stop nuts are less expensive than grade-C automation lock nuts. However, nylon will begin to deteriorate at temperatures from 150°C;-350°F.