Stop socket head screws from wiggling loose on equipment with constant, vigorous vibration, such as engines, turbines, and generators. These washers have a small diameter to fit under screws with narrow heads. Similar to a spring, they flatten under pressure to add tension between mating surfaces. As long as the washers aren't deformed or otherwise damaged, you can reuse them indefinitely without losing locking strength. Also known as conical washers and Belleville washers.

Stack multiple washers in the same direction to double or triple how much weight they can bear. Stack washers in opposite directions for better deflection, which means they compress further and withstand more shock and movement without loosening.

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.

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

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

Top-and-Bottom Serration—Adds friction for extra gripping power.