The Rislone Pelletized Radiator Stop Leak uses a proven formula that has protected hundreds of millions of vehicles worldwide since 1947. It features patented Rhizex pellets that dissolve in minutes to solve most common cooling system problems, including internal, external and coolant-to-oil leaks in radiators, freeze plugs, gaskets, heads, blocks and heater cores. It is specially formulated to seal larger leaks better than other stop leak products. It also conditions the cooling system, inhibiting rust and corrosion, lubricating water pump seals and helping to control electrolysis, all of which reduce the risk of engine failure due to overheating or poor lubrication. Rislone Pelletized Radiator Stop Leak (p/n 31191) is compatible with all brands of antifreeze, including conventional green or blue (silicate-based) and extended life red/orange or yellow (OAT/HOAT) coolant. It works safely and effectively on plastic, aluminum and metal radiators, heater cores, blocks, heads, gaskets and freeze plugs. Pelletized Radiator Stop Leak is available in case packs of six bottles.