Prestone Flush 'N Fill Kit professionally back-flushes cooling systems of most cars and light trucks on the road today. Easily installs anti-freeze/coolant in minutes. Rust and dirty coolant that circulates in your car's cooling system can lead to a clogged radiator, resulting in overheating and engine damage. Draining the radiator alone does not sufficiently remove old coolant, as the radiator may contain 40 percent or less of the coolant. The Prestone Flush 'N Fill Kit allows you to professionally flush the complete cooling system, not just the radiator, in one easy process.