The Thexton Disc-Type (EG) Anti-Freeze Tester, No. 106, is a professional disc-type 16-1/4" tester that is accurate at all temperatures, the company says. This tool tests eythlene glycol-based coolants, hot or cold, including Dex-Cool. The easy to read discs are magnified by a convex design of clear SAN plastic barrel. The tester can read in both Celsius and Fahrenheit scales. A notable feature of this tester is the "6th disc" that shows over protection and a loss of cooling efficiency. Beyond 70 percent anti-freeze, cooling and corrosion effectiveness is reduced. This tester is a one-piece bulb with a neoprene dip tube.