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.