Klein Tools Receptacle Testers are designed to detect the most common wiring problems in standard and GFCI receptacles. A convenient chart on the tester helps determine wiring condition in outlet, based on lights results. Conditions indicated: open ground, reverse polarity, open hot, open neutral, hot/ground reversed. For more than 160 years, Klein Tools has manufactured premium-quality, professional-grade hand tools that deliver the performance, durability and precision needed to get the job done right. Our family of engineers, workers and craftsman continue to put six generations of expertise into every tool we create by using only the highest quality materials, superior workmanship, and keeping manufacturing as close to home as we can. Klein isn't just the name of our company, it's also our family name. And since we're an American company that's family-owned and family-run, you know you can count on us to be here tomorrow. Klein Tools doesn't just make great products, we make great products that stand up to the demands of the professionals who use them every day ... Since 1857. EFFECTIVE GFCI WIRING PROBLEM DETECTION: GFCI Tester detects common wiring problems in standard and GFCI receptacles, ensuring electrical safety COMPATIBLE WITH GFCI OUTLETS: Works on GFCI outlets and verifies the proper operation of the ground fault protective device, providing peace of mind DURABLE AND TOUGH: Built to withstand a 6.6-foot (2m) drop, ensuring durability and reliability in various working conditions WIDE OPERATING TEMPERATURE RANGE: Can be used in temperatures ranging from 32-Degree to 140-Degree Fahrenheit (0-Degree to 40-Degree Celsius), offering versatility VERSATILE VOLTAGE SUPPORT: Designed for use with 110/125V AC at 50/60Hz in 3-wire outlets, meeting common voltage requirements QUICK AND ACCURATE TESTING: The GFCI Tester provides a fast and reliable solution for detecting wiring issues and confirming the functionality of GFCI outlets ENSURE ELECTRICAL SAFETY: By utilizing the GFCI Tester, users can verify proper wiring and operation, promoting electrical safety in homes and workplaces