I use these for desert hiking. I actually stay cooler when I keep the sun off , so I wear this shirt and a pair of polypro hiking pants. Shirt is true to size (M) for me.

I used to use hydration bladders for desert hiking, but I could never tell how far 'down' I was on water. Plus, on longer desert hikes with no water sources, I like to carry four liters of water. Now I use one of these bottles with the sucking straw cap, which has a drinking tube attached to it. I carry up to three of these bottles with the classic cap. When I drain each bottle, I swap the bottle for a full one and put the classic cap on the empty. As a result, I always know how my water supply is holding up without having to open my pack to check a bladder.

Just used one of these on a rim-to-rim Grand Canyon hike. 'Self-inflating' is a bit of an exaggeration, but a few breaths did it nicely--a very easy inflate. Actually, you can get it back in its sack, if you get absolutely all the air out of it. But it's still a tight fit. I was amazed at how comfortable this pad was, fiven that it is very thin. No reservations recommending this item.

Great pack. Just used one on a four-day, rim-to-rim Grand Canyon trek. Plenty of room for tent (Big Agnes Seedhouse 2), sleeping bag and pad, stove and fuel, food, snacks, water (3 1L bottles), clothes, sandals, and camera. Weighs about six pounds empty. The pack has a great suspension system, with an adjustable lumbar support and cinch straps to pull the load forward, off your shoulders. Carrying about forty pounds (including water), I had no problems with back or shoulder soreness. Bought my own as soon as I got back. No hesitation recommending this pack.