Bar's Leaks Cooling System Radiator Stop Leak Professional Strength Formula tablets inhibit the formation or rust and scale, neutralize pH imbalance, controls electrolysis, lubricates and seals internal, external and coolant-to-oil leaks. Same tablets as used by many OEM auto and truck manufacturers around the world. Bar's Leaks Radiator Stop Leak is designed to enhance the use of antifreeze or can also be used in water. When used in water alone, it is also recommended to use a cooling system anti-rust and water pump lube.