I bought the 35L medium size pack, I'm 6ft 180lbs and it fits me perfectly. I have tried out and tested the 50L Large pack and found it a little to much, so I switched down to the medium which was much better. If you're taller then 6 ft I would recommend the large. Overall a great 35L pack, the back suspension to keep the bag off your back helps when it gets really warm. I use this pack for camping, long distance cycling (50-100+mi), and usually out for a weighted ruck run (30-40 lbs). The integrated rain cover is excellent and does what its made for which beats out TNF bags that don't come with one. Some reviews complain about the straps being everywhere, but you shouldn't let that discourage you from this bag since they're easily tucked away. The two complaints I have about this pack is that when fully packed and loaded the top "hood" part of the bag barely pulls over the backside of the bag and can pool in water if you don't tightly pull it over the back suspension. It's a minor issue that hasn't really bothered me but is a slight annoyance. Also that when fully loaded with over 35-40 lbs the shoulder straps can slightly dig into your shoulders and become an annoyance on long hikes/runs, but very manageable. Other then that I highly recommend this pack since it keeps my gear dry and is not too large for what I need.