K2 RADIATOR STOP LEAK is the highest quality product for sealing radiators. Seals even large leaks quickly and efficiently. Ideal for stone blows. to remove leaks caused by vibration or other mechanical damage. Can be used in all types of coolers. It mixes with all types of coolant. including the latest long-life coolants. It does not prevent fluid circulation within the system. Safe for the heater and other cooling system components.