It has been used, but is in excellent condition (I would describe it as *very* close to new).
It has had one small alteration, the strap on the waist belt has been trimmed so that it doesn't hang down & get in the way. It should fit anyone up to a waist of size 40 quite comfortably though.
Size is Large.
From the manufacturers site:
http://www.ospreypacks.com/en/product/m ... ifications
Thru-hiking/Overnight to extended trips
The Atmos 50 provides the ideal volume for your next superlight backpacking experience. At 3000 cubic inches and with an average weight of just over 3 lbs / 1.5 kg, you can carry your superlight essentials with ease and comfort. A traditional floating top pocket/top load design and twin front pockets with welded water resistant zips makes loading easy. Other features include an internal hydration sleeve, zippered mesh pockets on the adjustable hipbelt and removable sleeping pad straps.
If anyone has any questions please ask.
Asking price: $130 ONO + shipping