Exactly! I do not have a government mandated Tire Pressure Monitoring System. I have a Tire ROTATIONAL Monitoring System which should technically violate the law. My 4 tires are not of equal tread depth. But so what? It is preposterous to required to buy 4 new tires of the same brand and tire depth when only 2 have less tread depth than the other 2. And what is a person supposed to do if they have one blow out, buy 4 new tires? I realize the indirect TPMS is cheaper to install for auto manufacturers but based on my experiance it is a inherently flawed Tire PRESSURE Monitoring System