Prestone Antifreeze/Coolant Tester is a professional do-it-yourself tester that easily tests for anti-freeze/anti-boil protection. It is important to maintain your antifreeze/coolant at the proper concentration to provide good corrosion protection as well as prevent freeze-ups and boil-overs. This tester provides a quick and easy method to safely collect a sample and measure coolant concentration. It also allows a visual inspection of the antifreeze while you test it.