Nylon insert lock nuts have a nylon insert. These locknuts are strong enough to use on most machinery and equipment that are prone to vibration and temperature changes. The nylon insert also wont damage the threads on your bolt. These nuts are reusable, but their holding power lessens with each use. Zinc plated fasteners have good corrosion resistant qualities and are a good choice for indoor, outdoor and industrial applications. Grade 8 is high strength for applications requiring superior load and tensile strength such as heavy duty equipment or machinery.