I don't know. This is presumably a non-lethal weapon for self defense. I must admit I don't always carry where it is illegal. This tool seems to be legal in most states however I doubt that I woud ever carry one. Personally where I can carry a pistol, I do. I also carry a large Mag-lite. It can do as much damage as a baseball bat at close range after you blind the assailant first with a powerful LED beam. IMO It is no different than learning how to crack a BG in the head with the butt end of a pool cue. Actually, I normally prefer to punch a BG with an uppercut to the bottom of the nose and then the throat. A roll of nickles in you palm and gloves can make a difference and you won't end up going to jail.
Saw a Sharkie at the gun show last weekend. My friend's son (16) was wondering what good it was for. I explained the idea of Kubatons to him and that the Sharkie made for a nice covert one....blank stares....
I told him to grab my wrist and then immediately put him in a wrist lock.
He's a believer now.
Joint manipulations take some training. Striking at pressure points and vital targets somewhat less so. As my TKD teacher taught me, it's always nice to have many arrows in the quiver. It also gives you options in the continuum of force.