12.5" long and rated for tanks up to 35 gallons. These are quality heaters at a great price. They are fully submersible and come in sizes 25-300 watts. They also have 2 sizes that are mini size to fit in those extra small tanks. All regular size heaters come with an easy to read and set dial. The mini sizes do not have this feature to save on the size but they have fully adjustable temperature settings. Comes with a manufacturers limited lifetime warranty