To ensure food is stored at ideal and safe temperatures this thermometer, CDN model# FG80 measures the precise internal temperature of freezers and refrigerators. Housed in a durable plastic casing the 4-3/4-by-1-1/4-inch thermometer features a red non-mercuric column inside industrial-grade glass. Two stainless-steel clips keep it securely fastened to a shelf. Temperatures read horizontally in a dual scale range of -40 to 80 degrees Fahrenheit (-40 to 27 degrees Celsius). Zones are marked for recommended storage temperatures: a freezer should be set ideally between 0 and -10 degrees Fahrenheit (-17 and -23 degrees Celsius) while a refrigerator should be kept between 34 to 40 (1 to 4.4 degrees Celsius). Colder than that causes lettuce to freeze; warmer and foods spoil too quickly. Certified by the National Sanitation Foundation (NSF) this thermometer has been manufactured to high commercial standards. CDN covers this professional thermometer with a five-year warranty against defects. 5-year warranty Thermometer tests freezer and refrigerator for safe food storage Measures temperatures from -40 to 80 degrees Fahrenheit (-40 to 27 degrees Celsius) Non-mercuric durable laboratory glass column reads horizontally Stainless-steel clips mount thermometer securely.