Hexagon nylon insert nut, stainless steel grade A4 (316) DIN 985. The hex nut has a nylon filled collar at its top 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. Also known as a nyloc nut, polymer insert lock nut or elastic stop nut.
