I will give 5 stars to the price for 5$, which somehow dose the job for cheap. The annoying thing is the head rest holders, they are not designed to hold the sides firmly, but you get what you pay for.
We have 2 cars that are, I imagine, pretty standard: 2011 Kia Sportage and 2005 Acura TL. The attachment does not fit on either one. We would need to tighten it a good half of an inch more than what it currently allows us to do. The built is good, and I am generally a happy customer of Monoprice, this is the only reason I give it 2 stars.
It feels solid and I had no issues fitting it in the car. Two small issues: it doesn't pivot at the base, so if your headrest bars are at a funny angle, the mount could be pointing down, meaning the viewer looks down (bad for car sickness), but it's pretty minor. Also, be aware the little nuts for the headrest tightening knobs are not secured and are prone to falling out into the depths of your car if you get overly enthusiastic with the knob loosening