Reassuring After-Sale Service, Free US flag patch. Ultra comfort and removable waist fasten system. Reinforced ventilation system on the back. Increased range of hook&loop. A comfortable lumbar fixation system has been added and is removable. 40L Military Tactical Backpack. Constructed of durable and water resistant fabric, and the waterproof and rainproof cover system over the main zippers. Reinforced triple nylon thread stitching ensure the bearing ability.