Safe to use and seals instantly. Stops coolant leaks, guaranteed. Contains Xtreme Cool which helps reduce coolant temperature. Stops overheating related to leaking coolant. Rislone Liquid Aluminum Stop Leak safely seals radiator, heater core, gasket and freeze plug leaks. Works with water and all antifreeze coolants. 1 bottle treats 4-6-8-cylinder engines. Simply add bottle contents directly to your cooling system. No flushing is required after application.