Professional disc-type 16-1/4 inch tester is accurate at all temperatures. Tests ethylene glycol based coolant, hot or cold, including Dex-Cool. Easy to read discs are magnified by convex design of the clear SAN plastic barrel. Celsius and Fahrenheit scales. Special feature is the "6th disc" which shows overprotection and a loss of cooling efficiency. Beyond 70 percent anti-freeze, cooling and corrosion effectiveness is reduced. One-piece bulb and neoprene dip tube.