A special radiator cap that includes a sacrificial magnesium anode that protects aluminum and other soft material engine components from electrolysis. Electrolytic Metal Erosion (EME) is slowly destroying your engine components. EME attacks timing chain covers, radiators, heater cores, intake manifolds, freeze plugs, head gaskets, thermostat housings even cylinder heads causing premature failures. By allowing EME to attack the sacrificial anode, the “Rad Cap” protects your engine while driving or in storage. Fits all years, concourse correct appearance for 1964 - 1966 S.M.C.O. stamped with fourteen pound rating. For a simple and inexpensive way to protect the engine, it’s “Rad Cap.”