The Square D™ by Schneider Electric brand Heavy Duty Safety Switch is designed to be tough, reliable and provide exceptional performance in the most grueling conditions; from commercial and institutional to industrial and manufacturing facilities. F Series safety switches provide significantly higher levels of mechanical endurance than NEMA KS-1 or UL98 standards require. The design life of a F-Series switch is a minimum of three times the NEMA requirement.H364RB is a Heavy Duty Safety Switch Fusable 600V 200A 3P NEMA3R This is a Single Throw Safety Switch complies to UL listed standards. This switch has a short circuit curent of 10 kA -200 kA. Fuse types for this Safety Switch are H or K R, J or L.