The Milwaukee Voltage Detector and GFCI Receptacle Tester Kit is built for the pro electrician. The Voltage Detector can be used for residential, commercial, and industrial applications. With the highest safety rating in the industry, CAT IV 1000-Volt, the Voltage Detector can detect a wide 50V to 1000V AC range. A red LED and an audible tone indicate the presence of voltage. The Detector includes (2) AAA batteries and is covered by a 1-year warranty. Our GFCI Receptacle Tester is designed to reduce the risk of electrical shock generated from outlets. The over-molded grip provides durability and comfort for all applications. Additionally, the visual indicator light turns on, indicating the activation of the GFCI test, if functionally correct. LED visual indicators help determine the wiring conditions of an electrical outlet. Wiring conditions indicated - hot and ground reversed, hot and neutral reversed, open hot, open neutral, open ground, and correct wiring.