Hit the throttle on your trail runs or mountain bike rides without uncomfortable pack jiggling or annoying water sloshing slowing you down. The smartly designed Osprey Rev 18 Hydration Pack feels like a natural extension of your back, staying securely in place while you bounce up and down the trail. The BioStretch shoulder harness and waist belt are designed to lie flat against your body and follow your movements like a piece of stretchy clothing, eliminating uncomfortable rubbing and chafing. Two sternum straps keep the pack from swinging side to side and to take a load off your shoulders, and can be adjusted or removed to suit your preferred position and pack fit. Quickly tighten or loosen the waist belt on the fly with the easy to operate ErgoPull closure, and control the volume of your load by cinching down the bungee cord webbing on the front of the pack. The mesh covered back panel, shoulder harness, and waist belt keep air flowing while you're working up a sweat barreling up and down the trail. The Rev 18 comes equipped with a lightweight 2. 5 liter hydration reservoir that fits in its own dedicated compartment, and is designed to prevent water from sloshing around while you move. A magnet on one of the sternum straps holds the drinking tube bite vale so you can quickly sip and then get the tube out of the way. Stash larger items like a rain shell, trail maps, or bike supplies in the large zippered front pocket or the bungee web on the front of the pack. Organize smaller items in the slew of smaller pockets around the pack like the drop down, removable media pocket on one of the shoulder straps to keep them ready at hand so you won't have to stop. From its overall design to its pocket placement, the Rev 18 is all about keeping you moving without anything slowing you down, so rev up your engine and don't look back.