These metal-backed thermometers have a V-shape design to help protect them from breaking. They have a glass tube but are mercury-free for safety so these are great for the classroom. Thermometers feature dual-scale temperature readings from -14-degrees F to 230-degrees F (increments of 2-degrees) and -33-degrees C to 110-degrees C (increments of 1-degree). Each thermometer is about 5-3/4 in. long. Set comes with 10 thermometers. For over 50 years, hand2mind has encouraged hands-on learning and discovery, driving deeper understanding and helping children unlock their full potential. With products designed to enhance learning in the classroom and the world around us, we strive to find new ways to encourage hands-on exploration and discovery.