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.

18-8 Stainless Steel—The choice for wet and outdoor environments, these washers won't rust when exposed to moisture. However, they can't hold up to the harsh chemicals that 316 stainless steel can.

Black-Oxide 18-8 Stainless Steel—Typically chosen for their appearance, these washers have a dark, matte coating to create a finished look. They won't rust in wet and outdoor environments, but can't hold up to harsh chemicals as well as 316 stainless steel.

Super-Corrosion-Resistant 316 Stainless Steel—Superior to 18-8 stainless steel, these washers won't degrade when exposed to harsh weather, salt water, and most chemicals.

Zinc-Plated Steel—A common choice for areas with occasional exposure to moisture.

Zinc-Yellow-Chromate-Plated Steel—With the same corrosion resistance as zinc-plated steel, these withstand occasional exposure to moisture.

Black-Oxide Steel—Typically chosen for their appearance, these washers have a dark, matte coating that creates a finished look. They offer minimal corrosion resistance, so they're best for dry environments.

Blue-Dyed Steel—These metric-sized washers have a distinctive blue color, so you can easily tell them apart from inch washers. The coating provides only minimal corrosion resistance, so these washers are best for dry environments.

Steel—Best for dry environments since moisture will cause these washers to rust.

Corrosion-Resistant Galvanized Steel—These washers combine the strength of steel with the rust resistance of stainless steel. They're an alternative to 18-8 stainless steel in wet and outdoor environments, but they won't hold up to salt water and chemicals.

Super-Corrosion-Resistant Zinc-Flake-Coated Steel—With 40 times the corrosion resistance of zinc-plated steel, these withstand rust as well as 316 stainless steel. They have been tested to extreme standards, including 1,000 hours of salt spray. They are similar to Magni-coated washers.

Aluminum—One-third the weight of steel, these washers are commonly used for assemblies that have weight limits. They're an alternative to stainless steel for rust resistance, but aren't as strong.

Super-Corrosion-Resistant Silicon Bronze—The choice for marine environments, these washers won't rust or deteriorate when submerged in salt water. They resist corrosion as well as 316 stainless steel, but are not quite as strong.

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.