Hi-Gear's commitment to providing only the highest quality products is exemplified in its offering of performance additives, fluids and treatments. Each and every product is engineered to meet or surpass the strictest of industry standard specifications. Hi-Gear maintains its own research and development facility and formulations are constantly under review to ensure the latest technologies are implemented. Radiator and Block Seal is safe for all engines - cast iron, steel and aluminum. It is safe to use in all radiators - copper, brass, aluminum and plastic. This highly concentrated formula seals leaks in engine blocks and heads as well as seals leaks in the radiator, heater core, freeze plugs, water pump and thermostat gaskets.