Its tested on the salesmen. I AM NOT JOKING.would have tried it on realistic dummies. prob catches the bullet like a net, stops full entry, still give you internal bleeding, broken bones etc. better than a bullet through the lung. In random gun fire the torso is the most likely to be hit.
head shots are for snipers and halo3. no point having one for the head. a harsh impact like that to the skull will crack it without entry. Stick with a tin helmet.