Gasket Gravity tank-to-bowl gaskets, hardware, and kits are components for installing new toilets or replacing worn parts on existing fixtures. Gaskets are rubber or plastic rings that form a water-tight seal at the tank-to-bowl connection. They deteriorate over time and may need replacement when they leak. Hardware components are nuts, bolts, and washers for connecting the tank to the bowl. They typically need to be replaced when they crack, corrode, or won't seat properly due to stripped threads.