Type "W" fuses are an older style fuse utilizing an Edison base and are all but obsolete. They are general purpose plug fuses and "fast-acting", that is they have no time-delay fuse element but will quickly interrupt the circuit once the rated amperage is exceeded.
The fuses are designed for use in general lighting and power circuits that do not contain electric motors. Electric motors draw additional current at start up and will blow these fuses if the motor is of any significant size. Because of this, time-delay fuses are now almost exclusively used.
Rating: 120 volts; up to 30 Amps