Selling to declutter! This is the SKYRC GNSS Performance Analyzer. It can accurately measure speed using GPS! You use it with an app on your smartphone. You can use it for radio-controlled cars and mini 4WDs, as well as measuring the error in your own car or motorcycle's speedometer, and more! You can find videos of people using this device on YouTube, so you might find them helpful (the manual is also in English). There is a small tear in the box, but the main unit has only been used twice, so it's in good condition. Please refrain from purchasing if you are looking for perfection or are overly concerned about minor details. Feel free to ask any questions or discuss shipping methods. I think it's a great price, so please consider it!