Heavy-duty Fustat S-Type time delay, dual element, plug fuse. Features a rejection base for critical circuit protection such as air conditioners, furnace blowers, swimming pool pumps, deep freezers, or any circuit where motors turn on and off frequently. Industrial strength, will not open under repeated motor start-ups. Porcelain threads (tamper proof base) prevent a larger amp fuse from being used. Extra large clear window makes it easy to see if fuse is blown. 125V AC, 10,000 A.I.C. UL (Underwriter's Laboratories) listed.