The back frame allows good ventilation if there is a slight breeze during a hike. Comfy and well designed shoulder straps. This is a great pack for hiking, but don't be fooled into thinking you can use this same pack for lugging textbooks around. The curved frame doesn't allow any sort of hard, rectangular items to be packed. Only soft flexible items, such as clothing, work well with the odd interior shape. The curved frame also steals a lot of room, making the pack seem bigger than it really is. Still, it works great for day hikes and surprisingly well for mountain biking. Rugged materials and good craftsmanship make this pack a winner.