Stop nuts and screws from loosening due to mild vibration. As you tighten, the uneven ends bite into the nut or screw so it won't back out. While they're not as vibration resistant as other lock washers, they are a great fit for electrical panels, light fixtures, and other light duty assemblies. Split lock washers are not reusable, and they only work with fasteners that have right-hand threads.

High-Strength Super-Corrosion-Resistant K500 Nickel—More than three times as strong as 316 stainless steel, and with superior rust resistance to withstand prolonged exposure to salt water and acids. These washers are often used in the oil and gas industries. Also known as Monel.