The fourth generation of Ospreys womens specific Aura ventilated backpack series features the Anti-GravitySuspension*. This 3D suspension system provides seamless comfort that contours the body allowing a trail experience like no other. Combined with custom capability and a full feature set; the Atmos AG sets a new standard in ventilated backpacking. The womens specific Aura AG 50 introduces the Anti-Gravity suspension* system to a new line of ventilated backpacks. This 3D suspension system contours your body providing seamless comfort allowing the user mobility with ease on any multi-day backpacking trip. *Osprey Anti-Gravity [AG] A continuous panel of lightweight mesh extends from the top of the backpanel to the hipbelt. The seamless structure contours automatically to the body; providing outstanding fit and unrestricted movement when wearing the pack. Sizing and Fitting of your OSPREY pack – Getting the Pack that’s right for you! Fit is the key to pack performance. Take the time to get it right. If you’re buying from our online store measure yourself carefully and don’t hesitate to email or call customer service if you have questions. Once you have selected the pack model that meets your needs; you will need to choose the right size. Step 1 – Pack Sizing Most of our Opsrey packsvare available in multiple sizes to fit a range of torso lengths. To find your torso length; have a friend measure your back along the spine (as shown in the illustration) from the level of your iliac crest (the top of your hipbones) to your C7 (the knobby bone at the base of your neck). Use the charts below for different osprey models to determine your pack and sizes. How to pack your pack: Be sure to use the red internal compression strap. Also; compress the contents solidly using the external compression straps. You want the pack to adopt a tall; thin profile. Remember to maintain side-to-side balance as well a pack that leans over to one side places excessive pressure on your spine and irritates your shoulders. Make a point of getting as much gear inside the pack as possible. Odds and ends strapped on all over the outside of the pack wreak havoc with balance; especially if they are free to swing around. Finally; the top pocket has a tendency to become the repository for many; many small items that add up to significant weight and often make the pack distinctly top-heavy be careful!