CAUTION: I was going to buy one of these (Stebel, Bad Boy are the same horn, I believe). However, I've found a lot of (non VN750) forum posts where they've died, most within a few months. WebBikeWorld ordered two to test for product reviews: one was DOA, the other gave two or three blasts and died. Not good. They also like to fall off, since there's only the one stud to mount a big horn.
They don't ALL die, but they seem to have a poor reliability record. It was enough to scare me away... I want the horn to be there when I need it.