This zinc-plated hex nut is made of heat treated steel and has a nylon-filled collar at its back end. When a screw reaches the collar, the threads and nylon form a tight, frictional fit, restricting movement of the screw when it is subjected to vibration. Common structural applications include engines, turbines, hydraulic cylinders, railroads and aerospace. For use with Grade 8 bolts with a minimum tensile strength of 150,000 PSI as well as in temperatures of 250 degrees (F) or below. NLN38F8