Flex-a-lite fan spacer adapters convert a variety of hub pilot diameters to a standard 5/8-inch pilot, and they provide the required spacing from the radiator. Our fan spacer adapters have a large bearing surface and are machined to a soft radius. This reduces point-loading, which is the most common cause of stress cracking on the fan center star. This is why we require that a Flex-a-lite spacer adapter is used with our fans. Flex-a-lite fan spacer adapters are machined from aluminum.