Do radar scramblers work?

I want to buy my boyfriend a radar jammer for his birthday. I have done research and this one seems legit a href="http://rockymountainradar.com/store/12-rmr-c435" rel="nofollow"http://rockymountainradar.com/store/12-r…/a but i'm not sure. Some people say that the people from the companys sneak in and write good reviews. Some people say it works, some don't. I really just don't know. If you have one, does it work? If you have this specific one, even better, does it work?