I have mixed feeling on this device.
it works pretty well if your dent is as follows
Newer car/pathy-many of the new vehicals use a grade of sheet metel that is thinner. this has 2 plus's to it. First pulling the dent is easier, second, there is less likelyhood of having a crease after.
Next is what type of ding/where its at. If it is a symetrical, ie round dent, it works well, but if the ding is oblonge you can end up with multiple pulls, this leaves a warped look, which in many cases is worst. Also if dent is at a crease, it will not work.
My 2 cents, Try and pull it, either way it will work, or it wont. if it's a replacable panel, such as fenders, hood, doors etc, search the scrapyards and look for a replacement(may have to have painted.)
in the end there is really no $20.00 fix that is a miricle. I have used this on my pathy and a couple other cars, and it worked maybe 1 out of 4 times, and even when it worked i have mixed results.