Mountainsmith Auspex 4200

This is the replacement for the old Mountainlight 4000. It's a bit heavier but the suspension seems to do a better job than anything in the 4lb or under class. It has a real hip belt (unlike many lightweight packs) and is very well designed.

The Auspex has a unique back pad scheme that leaves an open area up the spine for cooling and moisture relief. The light Kelty packs, and others, put either pack cloth or a thin non-wicking pad against your entire back which can be hellish in warm weather. The Auspex has both wicking mesh fabric and open areas.

I tried a lot of packs in the 3-5 pound and 3200-4500 cubic inch range. Some, such as the Arc Khamsin 52 fit well but are significantly heavier. Most don't carry a load anywhere near as well as the Auspex.

The capacity is perfect for an overnight with all the trimmings or an ultralight multi-day trek. The pack seems to be very well made and is highly adjustable. I especially like the "delta" dual hip snugger straps at the bottom of the pack which work much like those on the big Dana packs. You can really get the load in tight and make the hip belt work as it should. It also has "load lifter" straps on the shoulder straps to take the weight off the tops of your shoulders. Some lightweights are lacking these as well.

Downsides? The packcloth is kind of stiff (it's a special high strength lightweight cloth). The lid doesn't convert to a fanny pack. It only comes in one size which might be a problem for some but it fits me really well. Some think $250 is a bit expensive.