Schneider Electric's Square D heavy duty safety switch is designed to be tough, reliable and provide exceptional performance in the most grueling conditions. All heavy duty safety switches feature a quick-make, quick-break operating mechanism, a dual cover interlock, and a color coded indicator handle. They also come with many field installable or factory installed accessories. This fuse rejection kit is field installable and limits the switch to only Class R fuses. It is for switches rated for 400A to 600A. One kit is required for a three pole switch. It is UL listed.