Monitor refrigerator and freezer temperatures to optimize performance and protect against food borne illness. The durable, NSF Certified, professional quality, stainless steel thermometer conveniently stands upright or hangs from shelf. Dial measures 3.5". Refrigerator temperature range is 32(degree)F - 46(degree)F (37(degree)F default). Freezer temperature range is -6(degree)F - 6(degree)F (0(degree)F default).