Rislone Liquid Copper Block Seal Intake & Radiator Stop Leak seals larger leaks regular stop leaks won’t. One step formula permanently repairs larger leaks in radiators, intake manifolds & gaskets, heater cores, blocks, heads and freeze plugs. Use on cars, trucks, vans, SUV’s and RV’s. One “1” Step Sealer contains an antifreeze compatible sodium silicate liquid glass formula, so no draining of the cooling system is required. It will not harm the cooling system when used properly. Use with all types of 50-50 mix antifreeze including conventional green or blue (Silicate-based) and extended life red/orange or yellow (OAT /HOAT) coolant.World’s Most Trusted Stop Leak Brand Since 1921 Permanently Fixes Cooling System Leaks Antifreeze Compatible—No Draining Required One Step—Pour Directly Into Radiator—Easy To Use