I just purchased and am just returning the pack as it is too shallow from too back to accommodate a full 3 liter hydration bladder and a compressed three season sleeping bag, mountain hardware 2nd Dimension. I bought the pack specifically as a two or three day, light weight, hydration compatible, sleeping bag compartment and when I tried to load the pack for my first use the items don't fit. I was going to a dry area and had to pack in a full three liter bladder and four, one liter bottles. Much too my surprise my sleeping bag would not fit. I seriously doubt if the pack is actually 3500 cubic inches. I suspect it is closer to 2800-3000 in the main compartment. The pack description and reality just don't match up. Too bad the price, features and fit are great. Its a size thing.