They work "OK".
Basically a half wave antenna, which doesn't require a ground plane, so it's going to exhibit 0dbd.
They are about 40 inches tall.
You cannot use them with many types of tinted glass, and you need to mount them away from defroster wires.
Then there's the $90.00 part.
I knew a guy a long time ago who had one on an older Mercedes sports car. It worked OK, and it was mainly because he didn't want to drill a hole. I get it.
But after a long time doing this stuff, I've learned that drilling a hole is the way to go.
I did use a UHF version on my wife's car back in the early 2000's. Not impressive, but it worked. I've never used one since, though.