The Square D™ by Schneider Electric brand heavy duty safety switch is designed to be tough, reliable and provide exceptional performance in the most gruelling 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. An abundance of copper is used in the heaviest current carrying power paths of all Square D™ by Schneider Electric heavy duty safety switches. The more copper for current carrying paths, the lower the temperature rise. Managing temperatures inside the switch is the key to providing greater service life. All heavy duty safety switches feature a quick-make, quick-break operating mechanism, a dual cover interlock and a color coded indicator handle.