Added to an old car that does not have a tire monitoring system. Good installation guide. Did what it said and it started reading within a minute of installing the tire sensors. This unit reads within a pound of my gauge (was pressurized before I installed the gauges). The only thing I didn't understand was rubber boots. Do they fold over the sensors or just cover the bar of the hoop? The two bad things I noticed are that you have flimsy nuts that have to be slid behind the sensors and then screwed onto the sensors. It's a flimsy key and if lost you will likely damage the sensors trying to remove them. Second, you need to remove the sensors to add air to the tires. But I guess since you see the pressure all the time you don't need to worry until it gets low. π It's good that the tire sensors have replaceable batteries, but the main unit doesn't. Fairly simple instructions for adjusting the signals of the high and low tire pressure sensors and high tire temperature sensors. Either Celsius or Fahrenheit. Also battery level indicator. In the pictures you can see a thin key and a handle to get closer to the size of the main unit. In case you haven't noticed, it's on all the time. It runs on solar power and hasn't died yet. (@6 weeks from install) If it doesn't work, it has a USB connection. Not a small connection, but a larger one. Like most connections for car GPS devices. Hopefully it will also charge if left in the sun long enough. If I had to do it again, I would look for a larger display.