Eaton Bussmann Fuse: 4 A Amps, 250V AC, 10kA at 125V AC/200A at 250V AC, BAF

Fast-acting, nonindicating midget fuses open within seconds of being exposed to overloads and short circuits. Also called fast-blow midget fuses, they are highly sensitive to changes in current flow and don't tolerate temporary overload currents or power surges. They have no indicator for identifying a blown fuse, so they're sometimes used with an indicating fuse block or cover.

Midget fuses supplement the primary branch-circuit fuse or breaker to provide backup overcurrent protection for lighting, solenoid, motor, and transformer circuits. Also known as 5AG fuses, they have lower interrupting ratings than branch-circuit protectors. They are noncurrent-limiting, so they won't limit exposure to the full magnitude and duration of an overcurrent.