This is a power supply tester to test your power supply if it works or not. Have a power supply that you don't know if it works or not. This is the easiest way to test out your power supply before you put it in your computer. The easiest and quickest way to test the condition of your power supply. It's easiest as plug and play. Just simply plug the tester to your power supply ATX Motherboard power connector. The LED light on the tester will show up and give you a basic diagnostic of your power supply. All green LED light up means the power supply is good to use, and if a red light appears consider the power supply is no longer usable. This will prevent accidental damage to your computer. It has a built in 25watts 5.4-Ohm load generates steady output.