6100 cu in, 100 liters. (also see a medium measured as 6468 cu in, 106 liters). At 7 lbs 8 ozs it's not a lightweight, but it's amazingly comfortable fully loaded. Conforms to the body and distributes weight comfortably. Gregory says the medium is for torso 18-20". Shoulder straps and hip belt positions adjustable.

Top lid converts to day pack - very handy after hauling all your gear to base camp. Bottom access. Lots of features to mount skis & gear. There's nothing you can't put in or attached to this pack. Gregory produced this pack for years while the rest of their line and other makers started downsizing packs. It may be the only big sturdy hauler around at this time. It's getting harder to find expedition packs. New ones are not as durable. They save a little weight but mainly by flimsier fabric, no fanny pack and smaller volume.

With more than a dozen other backpacks, I finally am thinning out garage and admitting I won't be doing this kind of traveling anymore as much as I hate to get rid of it.

Here are a couple links for more info and photos:
http://gregorypacks.com/en/GM68738.html
http://www.amazon.com/Gregory-Denali-Pro-Mountaineering-Pack/dp/B001EPPJB0
http://www.backcountry.com/gregory-denali-pro-backpack-6450-cu-in

New this cost $550 or more. Selling mine in excellent condition - no damage and totally clean and good looking. For $99

Thanks, James