From the front it looks like a simple daypack, but turn it around, examine the suspension and this backpack is built for comfort and performance. The Osprey Stratos 18 daypack features the sophisticated AirCore suspension system, designed to carry the load comfortably. Air circulation to the back is excellent, especially noticable when the conditions get a bit too warm. A sewn-in contoured spacer mesh shoulder harness and padded hipbelt also contribute to the stable, comfortable carry. The Osprey Stratos 18 backpack also features large panel-loading access for easy packing and reorganizing and multiple options for carrying hydration vessels, including an internal hydration sleeve with dual exit ports and two stretch woven side pockets, perfect for water bottles. Just right for day hikes and mountain biking, the Osprey Stratos 18 backpack is built to last thanks to Osprey's meticulous attention to detail and choice of advanced materials. This pack is also available in the slightly larger Osprey Stratos 24 and a slightly smaller Osprey Stratos 12.