https://www.superiorwasher.com/washers/9155/Military-Flat-Washers.html
Click this video to learn more about a type of washer used specifically in military applications. They are called military flat washers — so called for the same qualities / traits that are descriptive of the military — strength, consistency, and high quality.
Mil-spec refers to military specifications and military flat washers should pass stringent mil-spec criteria in order to qualify for use in high-stress applications and severe conditions. Long-lasting performance and reliability are the foremost requirements for this type of washer.