So I was at the shop a few days ago getting a new front tire and a few other things. When I went to pick it back up, one of the mechanics noticed my horn didn't work, and discovered the actually horn was too corroded to work anymore. I had already paid my bill and such so I was about to leave without dealing with it, when he stopped me. Turns out he had the horns off a totalled Goldwing in the garage, and he installed it on my bike for free. It's nice to find a shop every once in a while that ain't trying to take all they can get.
Anyway, I recommend this upgrade to folks with a "meek" stock horn. It has about the same footprint as the stock disc looking ones, but it's probably about 20-30 dB louder. There's actually two I believe, with two different frequencies, if you have mounts for two units.