I've had a Delta AirZound bike horn since 2012. I chose it because it is both loud and low-pitched, similar to a car horn. Small electric horns can't produce a sound which is both loud and low-pitched – it's physics, they can produce a loud and high-pitched sound, or a low-pitched sound which isn't loud and therefore worthless as a bike horn. I have small electric horns on some of my bikes which are amazingly loud (albeit high-pitched) but on any bike on which I can easily fit one, I install a Delta AirAirZound. Nothing else I have tried comes close to getting the attention of motor vehicle operators. I don't know if it's saved my life but it's definitely saved me from getting hit a few times when a distracted driver slammed on the brakes or otherwise took evasive action when hearing the AirZound horn.(I have not yet tried the Loud Bike Horn Mini, a battery-powered horn which produces a sound which is both loud and low-pitched like a car horn. It is large, it is expensive, and the battery requires frequent recharging. It is tempting, though, for those bikes which will not easily fit an AirZound.)The Airzound is easy to install: Find a place on your handlebars with enough room for the trigger and horn combination (this is the hard part for some bikes) and in a place where you can easily reach the trigger. Then put the air reservoir (the bottle) into one of your bottle cages. You can also use velcro or tape or other methods to put the reservoir in a convenient location. The air hose between the reservoir and the horn is pretty long but you can purchase an extension if you need more length.Then pump it up! The Airzound has a Schrader valve underneath the plastic trigger button. Flip up the plastic trigger, attach your pump, and add air until you reach 80PSI. Do not go much over 80 PSI! The bottle won't burst but the various seals on the bottle and inside the horn itself are not designed for higher pressure. If you overpressure the reservoir the seals will eventually begin to leak which means the AirZound won't hold pressure for very long. My first AirZound is over 6 years old and the seals are still perfect even through hot 7 hot summers and 6 cold winters so far.It's possible to adjust the volume of the horn with a little plastic dial but even at its lowest volume it is still pretty loud, far too obnoxious to use on pedestrians or other cyclists. Get a fun squeeze-bulb horn or a bell to use in most situations. But when you need to get the attention of a motor vehicle operator or some booby jogging backward with a pair of earbuds blasting his cranium, well, give 'em a blast of the AirZound – that's what it's for.I've never run out of pressure during a single ride. I suppose it's possible but I do ride on NYC streets and it hasn't been a problem. I am quite disciplined about checking the pressure at least once a week and adding some pressure after a ride if I used the AirZound at all. If you check and top off the pressure of your tires every couple of days just add the AirZound to that routine and you should be fine.The biggest problem is usually finding a place to mount the horn itself. The trigger is integrated into the horn, it cannot be separated. The horn isn't huge but it does require some space and must face forward to be useful plus you can't put it in a spot where it will blast into your own ear when you're riding; your bike might not have a good spot to mount it. And of course, since you will want to easily use the AirZound in an emergency situation, the horn has to be mounted in such a way that the trigger can be used when you're in panic mode – it you have to reach for it or it's in an awkward spot, it's not going to do you much good.I wish Delta would produce a version of the AirZound with a remote trigger of some sort. Being able to mount the horn in one spot and the trigger in another (right under where I rest a thumb on the handlebars) would allow me to put an AirZound on any bike rather than just a few.Recently, my 6-year-old AirZound's plastic trigger/cap broke. I was able to hold it together with some tape but really needed a replacement. I wrote to Delta and they sent me two replacement trigger/caps and these trigger/caps have a new design which is both simpler and less likely to become damaged over long term use. That's great customer service and it's nice to see the product is receiving continued development.