Review on Gozens 26-80psi TPMS: Accurate Tire Pressure Monitoring with Valve Stem Cap Tyre Sensor Indicator (32 PSI) by Andy Tunes

I bought 50psi for my mountain bike because in a few weeks I need to top up for some reason. I inflated the tires to 50psi, which is decent for road use (45-60psi). After a few days the tires were soft but the hubcaps were completely green. I took them off and the gauge read 37psi. I ran an experiment: the caps show green until they drop below 36psi. It's too low. Red - 25 psi (out of 50). I went back and read the description and saw where it says they are accurate to within 20% for green. Well, 37-40psi is about 20% of 50psi. I just keep checking them manually. They will tell you your tire is flat, that's all. A look at the tires also reveals this.