Klein Tools ET250 Is A Solid-State, Digital Voltage and Continuity Tester. It Measures Ac/DC Voltages Up to 600V and Tests For Continuity. Additionally, The ET250 Tests Gfci Protected Circuits to Verify That The Gfci Device Is Functioning Appropriately. The Tester Includes A Backlight and Integrated Flashlight For Working In Reduced Ambient Lighting Conditions.