The Nylon Insert Nut is manufactured from grade 8 (high tensile) steel with a zinc and clear finish to help prevent corrosion. Nylon Insert Nuts, or Nyloc nuts are nuts with a nylon insert that lock the nut in place when tightened, the nylon collar of the nut squeezes onto the thread, holding it in place. This method prevents the nut from loosening and they are unaffected by vibration.