If you are mounting it on an XM the mounting hardware is already on your sled. You just pop the windshield off and use the screws under the windshield. It shouldn't take you longer than 5 minutes to put it on. You can hold a few bottles of water and some snacks that's about it but I really like it and money well spent.
I have the bag on mine, not lots of storage but additional storage is always welcome. The bag does interfere with the glovebox access especially when you have the bag right full.
Another option, the Holeshot dash bag, you remove the glove compartment door and it fits inside, the rest hides behind the windshield. Just checked ( not Fleece lined), has a clear window for your gps/ phone, and triples your storage capacity, quality zippers.
This will be the third year I am using my bag. I like it. Ya about 2 water bottles, and a pair of gloves or something like that. I like to use it for quick access stuff. It is really durable, i have rolled my sled over many times and it has never came loose. Same with branches and that its tough. You use the 4 bolts from your instrument gauge plastic that bolts to your head light frame. They eyes of the holes have steel rings so they don't tear. even when its full you can access the glove box compartment, its a bit tighter but you can still pull out your goggles.