The Cooper Bussmann 40 amp Brass Cartridge Fuses are CSA and UL listed. The cartridges are intended for use in light duty, general purpose circuit applications. The 1 time fuses are non current limiting, class K5 and rated for a maximum load of 250 voltages. For use in light duty, general purpose circuit applicationsClass K51 time fuseNon current limiting40 amperage250 volt