So what exactly does it do that stops the dog from barking?
I would not use it and I don't know if it works, I don't like things that suppress normal behaviors. Dogs bark, of course it's annoying so instead of suppressing it you need to teach them how much is OK and when they can do it (when you say speak, and they can bark two or three times when someone comes to the door) and make them want to follow the command (food). I would not sell that product if I were you because of how I feel about such products.