Klein Tools Receptacle Tester GFCI. A convenient chart on the tester helps determine wiring condition in outlet based on lights results. Specifications for Klein Tools GFCI Receptacle Tester: Manufacturer: Klein Tools Color: Black Features of Klein Tools GFCI Receptacle Tester GFCI Tester detects the most common wiring problems in standard and GFCI receptacles. Works on GFCI outlets and confirms operation of the ground fault protective device. Built to withstand a 6. 6-foot (2m) drop. Operating temp: 32-Degree to 140-Degree Fahrenheit (0-Degree to 40-Degree Celsius). Nominal Voltage: 110/125V AC at 50/60Hz in 3-wire outlet. Package Contents: Klein Tools GFCI Receptacle Tester Klein Tools RT210: Receptacle Tester GFCI