My sled didn't have the rail on the tunnel, so I had to mount d-rings on the sides of the tunnel. Once the d-rings were mounted, the bag worked pretty well. No problems with falling off. It would be nice if there were straps inside to secure loose items. Other than that, I am satisfied with the product. And it cost 1/2 as much as a factory ski-doo bag.
In my sledding group, I am the one who carries the extra supplies. This bag is the best I have bought so far. Holds a lot as it does expand up. Easy access. Zipper pulls can be used with your gloves on. Very sturdy material. Easy to put on your sled and easy to remove. Would have liked a handle for carrying it. SnoBunge is a reliable company that backs up their products.
This is a great bag for storage at a great price. I use it to carry food, water, and even a snow bungee. The best part about this is that when it gets hot out you can shed layers and expand the bag and throw them in the bag.