Canton Racing coolant expansion fill tanks are built with .100" thick aluminum. They have billet aluminum necks with a barbed overflow fitting and accept standard radiator caps. Expansion tanks provide an air space for the coolant to expand into and are required in all applications where the top of the radiator is lower than the top of the engine. These Canton Racing coolant expansion fill tanks should be mounted higher than the engine and radiator to ensure that the engine and radiator are completely filled. The tank itself should only be partially filled to allow for expansion. They have built-in mounting brackets, and an overflow hose can be connected to the filler neck barbed fitting