The Airzound horns are great, I have one on each of my builds so far. I usually give it a toot to let people know I'm coming out of a blind spot (big trucks) or around a blind curve/intersection. And to get people to move back from the bus stops a little when I'm heading for the bridge (no choice but to be on the sidewalk to cross the bridge I travel on, signage says for cyclists to use sidewalk only - besides, bridge speed limit is 80kph, and a lot of heavy traffic). I usually only use about 40 or so of the 85 psi the bottle holds any given week, but if I need it I can slap the air pump on it and fill it again.