This is not such an exciting product, but extremely necessary. The rain coat when folded takes up a really small amount of space in one of the pockets of your violin case. Then when you get hit in a rain storm, you open it up and hook it around your case. It wraps really neatly around my violin case and you can feel safe that no rain is going to get to hit your case.
The material is really water resistant and I've been caught in a few downpours and the outside of my case remains totally dry. My case is actually waterproof anyway, but this extra rain coat just gives you the peace of mind that your violin is going to stay totally dry and hopefully not even change the humidity level inside.
If you have an expensive violin, this is one of the best insurance policies that you can take out on it for when you're caught out in the rain. Even if you don't have an expensive violin, why would you want it to risk getting wet? Of course you wouldn't want to risk that, but with this super value rain coat, the thought wouldn't even cross your mind again. One of the best and economical investments you can make to protect your instrument.