With water temperature being such a critical factor for the well-being of fish, it?s important to have a good thermometer. This Marina LCD vertical mount liquid crystal thermometer provides accurate and easy to read temperatures readings in Fahrenheit and Centigrade. Ideal for all fresh and saltwater aquariums, the thermometer comes with an adhesive backing that makes mounting to the outside glass easy. Temperature ranges for this model: 18 to 30 C (64 to 86 F). Length: 4.45 cm (1.75 in) Other sizes available : 11220 Marina LCD Aquarium Thermometer, 20 to 30 C (68 to 86 F) 11221 Marina Horizontal LCD Thermometer, 20 to 30 C (68 to 86 F) 11223 Marina LCD Aquarium Thermometer, 7.6 cm/3 in, 19 to 31 C (66 to 88 F) 11226 Marina LCD Aquarium Thermometer, 7.6 cm/3 in, 19 to 30 C (66 to 88 F) 11227 Marina LCD Aquarium Thermometer, 8.6 cm/3.375 in, 72 to 86 F),