Built for a full day of motion, the Osprey Stratos 18 backpack featuring the AirCore suspension keeps the air circulating behind the back. Even the most driven hiker will notice the increased range of comfort when the temperature rises. Hydration options are also abundant on the Osprey Stratos 18 daypack. Bottles fit nicely in the two stretch woven side pockets and a hydration bladder conforms nicely in the cavity immediately behind the AirCore suspension. Yet another option is to place a bladder in the internal hydration sleeve and then routing the tube out one of two exit ports, depending on personal preference.