A cylinder fuse is a type of electrical fuse. Like other types of fuses, it is a safety device used to protect electrical devices from excessive current. As its name suggests, a cylinder fuse is shaped like a cylinder. It has a thin wire or metal alloy strip in the middle, and two metal caps, one on each end, which are used as contacts when it is inserted (in series) into an electrical circuit. The thin wire is designed to melt at a specific temperature which is reached when the circuit is carrying more than the intended amount of electric current. When the wire melts, the circuit is broken and no electricity flows.