THIS IS AN ORIGINAL MK BRANDED EMERGENCY LIGHTING TEST KEY/AKA FISH KEY. The Original MK Test Key for Emergency Lighting Grid Switches 3405ZIC Switch is a metal tool designed specifically for testing emergency lighting grid switches. Manufactured by the reputable brand MK, this key features a light switch port type and is essential for ensuring the functionality of emergency lighting systems in a business, office, or industrial setting. This product provides a reliable and efficient solution for maintaining and troubleshooting electrical equipment and supplies.