Robinair's No. 40859 Pocket Dial Thermometer is perfect for checking automotive, home, or commercial A/C and heater performance at the vent. Included pocket-clip carrying case protects the thermometer when not in use but keeps it handy for easy access when you need it. Adjustable design ensures accuracy - simply twist the thermometer face to a known temperature to calibrate (32F ice water works well) while holding the 10 mm nut at the base of the dial with a wrench. Compact, yet easy to read, black on white 1" dial face reads -40 to +70 degrees Celcius. Robinair, a Bosch Automotive Service Solutions brand, is a global leader in service tools and equipment based in Owatonna, Minnesota. Robinair is recognized throughout the world as the quality and performance leader in AC/R evacuation tools and this position has led to its success with the full range of products that serve the heating/ventilating/air conditioning/refrigeration (HVAC-R) and mobile markets, which includes the automotive aftermarket along with other industries such as agriculture and construction.