Hydration Backpack - Lightweight Water BackpackBreathable Mesh Shoulder Straps: Equipped with the ventilated mesh shoulder straps on this water backpack for air circulation, keeping you cool and preventing discomfort due to accumulated heat. This adjustable shoulder strap is made of silica gel, which is more comfortable to wear than cotton. Minimize pressure with its ergonomic design. This running hydration vest is lightweight enough to make it comfortble when running, hiking, cycling, biking,