Amp-Trap® 2000 A4BQ fuses are 20% 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 s time delay characteristic (at 500% of rated current) accommodates harmless inrush currents with no nuisance opening.