Replaced my Mountainsmith Mountainlight backpack after 15 years of use and thousands of miles(Backpacker backpack of the year 2001) with the Exos 38. The Exos is a sweet pack, it hugs my back tight, it's lightweight, and great ventilation along my back area. After many hours on the trail I barely feel it on my back. The only downside and the reason for the four stars. The pack protrudes so high above my neckline that when I look up during steep/scrambling conditions, the back of my head hits the back of the pack, limiting my area of vision. I've tried to see if the straps are adjustable and they don't seem to be. So if there is a route that consists of steep climbing conditions I will leave this pack at home and take another for safety concerns. Other than that I highly recommend this pack.