Works well. Not too hot, but definitely effective. My dog wraps himself up in this in the back of my car while I'm at work (3 seasons of the year). I find the spring on the cigarette / 12v outlet to big a little bit strong (squirts out of the outlet 1/8", which it wouldn't do if the spring were weaker/shorter), but it mostly stays in the outlet. The first one broke after 3 weeks, and Amazon replaced it. The second one has given us no problems. On a future production run, they need to shorten the length of the spring inside the outlet plug.