I bought a set for my wifes car (Ford 500)about a month ago(I think they were 36 or 38#) filled all tires to recommended spec 44# low pro tires.
yesterday while going over to visit my parents I noticed that 1 was red , she had picked up a nail !
had these not have been on there she probably would have a flat b-4 knowing it.I would not put them on my car (see avvy) but they look OK on hers and she loves them.
it is a great way to visually check and see if your tire is low b-4 you get into trouble. so, I would give them 1 thumb up.
they would've gotten 2 thumbs up if they made them in more variations. as I'm not keen on running the tire 8-10#'s under before you know it's low.
in a nutshell it's cheap insurance. but ,you should look at them each time you drive the car
HTH