Know how cold you can go. Thexton professional-size (16 1/4) tester is accurate at all temperatures -Tests coolant, hot or cold -Easy to read discs are magnified by convex design of the clear SAN plastic barrel -Protection scale is printed in both Celsius and Fahrenheit -Beyond 70% anti-freeze, cooling and corrosion effectiveness is reduced -One-piece bulb and neoprene dip tubThis large professional-size tester is accurate at all temperatures and is used to test coolant, hot or cold. It has a special feature, the 6th disc shows over protection and a loss of cooling efficiency. Made with the durability to last. $11.50.