Amp-Trap 2000 A4BQ fuses are more current limiting than any other Class L fuse on the market. When correctly coordinated, they bring a superior level of protection to service entrance equipment. Downstream circuit components have maximum protection against short circuit let-thru current. A4BQ's built-in 4-second time-delay characteristic (at 500 percent of rated current) accommodates harmless inrush currents with no nuisance opening. 600 Volts 4000 amps A4BQ series.