This useful and necessary TRIPLETT Commercial and Residential GFCI Receptacle Tester is a tool for residential and commercial electricians, home inspectors, and DIYs. You can detect faulty wiring in 3-wire receptacles. Lights display 5 wiring faults: Open Ground, Open Neutral, Hot/Ground Reverse, Open Hot, Hot/Neutral Reverse with an easy-to-read fault label on both sides for receptacles with ground up or ground down installation. At the push of a button, you can test GFCIs for proper operation. Unique 'Loop Design' allows for easier 'pulling' removal when testing is complete. cULus Listed.