Besides what comes in the box, you need to purchase 1 6mm spring/lock washer and 1 6mm 1.00 pitch nut, both preferably stainless.  These will be used to mount the compressor when used with one bolt from the stock horn installation.

Installation is fast, 1 hour or less.  Compressor mounts where the stock horn bracket attaches and the new horn bracket bolts onto the frame just in front and above the toe shift pedal.

Sound is quite loud, not overly so, but not deep and resonant.  Fitting the big horn on a Vulcan would require finding a new mounting point since the trumpet is quite long.