Based on the type of overcurrent the fuse is protecting, it will either need a full range or partial range fuse. Fuses offering short-circuit protection only are partial range and those offering both short circuit and overload protection are full range. The UL and IEC Standard has a nomenclature for these fuses called utilization class. It is a two letter symbol where the first letter denotes range of operation: ”a” for partial and ”g” for full range, and the second letter denotes the application protected. The designation R is for semiconductor protection. High-speed fuses are mostly partial range fuses that fall under Class aR, offering short-circuit only protection to semiconductor devices.