Features: Test computer power supplies with this simple power supply tester. It checks to the voltage on all wires to ensure that the power supply is functioning properly. This is an essential tool for any computer technician. It will allow you to quickly diagnose or rule out problems with the power supply, which should the the first thing you check when diagnosing computer problems. Please note that some cheap power supplies do not provide -12V power. Specifications: Component:ABS+Electronic Size:Approx.10x8cm/3.93x3.14inch Package Includes: 1Pc Power Supply Tester note: 1.Please allow 1-2cm errors due to manual measurement, making sure that you not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual of the item.