The Pentek o-ring seals the high temperature slim line housing canister and the high temperature housing top to prevent leaks in the water filtration system, The Pentek o-ring gasket should be well lubricated with silicone lubricant to prevent leaks in the water filtration system, The Pentek 237 FDA Grade Silicone Gasket should be used with the Pentek 10 Slim Line High Temperature Housings and the Pentek 20 Slim Line High Temperature Water Filter Housings, SKU: CWD1674