The sensor on this device is not good. Sometimes the PSI readings are close to accurate, but more often than not they're doubled A LOT! As a bicycle mechanic, I inflate bicycle tires all day. I noticed that some of my tires seemed to be too tight and started popping a bit. Checked with a high quality digital pressure gauge and YES! At a pressure rating of 35 psi on this unit, the digital pressure gauge reads 65 psi. I inflate tires to 20psi with this unit and the digital gauge reads between 35-40psi almost all the time. This block is inaccurate scrap!