This is a piece of junk. The product feels cheap and the buttons to turn off and change units are right where your fingers want to be. You have to pull as hard as you can to get it off the presta valve, which tends to cut your fingers into the cog, or at least some of the spokes, at high speed. In addition to blood from the joints, this device also releases a lot of air when reading. Sometimes it just works, sometimes you don't get a reading no matter how you tilt it. While I've had better luck