How to solve shopping cart rage when the aisles are too crowded with carts This fantastic little horn has been my goto solution for solving the problem of crowded aisles in the grocery store. Here is what I love about this horn: You can’t beat the price It can be used when your out walking or biking to make sure cars can see you or to scare runners It is a great story piece, people are always asking me about it It is small, I mean small, it fits in my hand It runs on a 9 volt battery so you won’t need compressed air It is water proof You can tap it lightly and get a smaller sound for indoor use Its always fun to have a good story, and this horn has given quite a few over the last few years.