Maintain the washdown rating of your enclosure, even after drilling holes in it. These washers protect against high-volume jets of water, as well as dirt, ice, oil, and coolant. The flexible rubber layer compresses to fill gaps, while the metal backing stops the washer from squeezing through the hole. Reuse these washers a handful of times, as long as the material isn't damaged.

18-8 Stainless Steel and EPDM—The best choice for outdoor environments, these washers withstand long-term exposure to sunlight, rain, and ozone.

Eliminate nooks and crannies under the nut or screw head where dirt and bacteria could collect. Unlike other bonded washers, the metal ring nests inside the rubber layer, creating a smooth outer surface that's easy to clean. These washers stand up to harsh cleaners and detergents and won't corrode from frequent washdowns. They're commonly found on equipment in food and pharmaceutical processing plants to prevent leaks and block out contaminants. Reuse them a handful of times, as long as the material isn't damaged.

316 Stainless Steel and EPDM—These washers are highly resistant to tearing, scuffs, and scrapes. They are more economical than Fluoroprene Fluoroelastomer, however, they aren't as heat resistant.