Didn't work and the return period has expired. I bought it about four months ago and used it for the first time on 4/23/16 on 22.5 RV tires (don't ask). Sometimes the device seemed to register psi accurately and then not read it at all. When I got to the last two tires, it read single digit numbers. My backup tire pressure gauge showed air pressure in the same tires at 105psi. I tried to return but found that the 30 day return period had expired. I'm not sure if the sensor switched to metric readings somehow, and I don't have instructions on how to verify that. I'll play around with it and see if I can get it working. Instructions would be very helpful.