About a year and a half ago I returned to the snow country and found that I needed an extra set of winter wheels and tires for our cars. I love the TPMS idea and driving all winter with a tire sensor warning and no pressure reading was unacceptable. Bottom line: 4.5 stars if Revain would let me. A very powerful tool that works great if you know what you are doing. The printed manual is very, very poor, both written for an older version of the firmware and apparently translated from another language with varying degrees of success. However, the quality of the instrument, body and accessories is very good. It requires a bit of technical and automotive knowledge to understand, but it does what it's supposed to do very well.