The OSPREY EXOS series is their lightest full size backpack at 2 lbs. 12 oz. for size Large. I bought an EXOS 58 from REI this year and have found it the most comfortable pack I've ever used, and that includes my heavy Dana Designs Terraplane. The EXOS 58 is 58 liters in size Medium and 61 liters in size Large. It is made to easily carry 40 lbs. without straining anything (except the hiker ;o). I've carried 48 lbs. with no problems. (I have added aftermarket side pockets and a front "wet rib" 5" X 8" zippered pouch with a bottle holder on one end that attaches to my lower shoulder strap webbing on each side. It's a belly pouch where I keep map & compass, bug dope, small headlamp, etc. and a bike bottle for electrolyte drink.) As a geezer I need to keep my gear weight as low as possible, especially since I'm carrying a scoped Browning A-Bolt rifle, ammo, 10X LRF binoculars, butchering gear, etc. PLUS I'm in northern Nevada's Ruby Mountains "at altitude". (7,000 ft. minimum) My light weight hunting gear list: 1.PACK-> Osprey EXOS 58 (W/ Camelbak hydration bladder & hose) 2. Tarptent Moment DW solo tent (2 lbs. 3 oz. W/ ripstop inner)(MSR Ground Hog stakes) 3. Western Mountaineering Megalite down bag (overstuffed and W/ mummy-shaped down top quilt) 4. Thermarest Prolite mattress W/ 3/16" thick foam pad on top. 5. Trail Designs Sidewinder titanium stove (ESBIT tablets or wood for fuel) 3 cup aluminum pot & "one egg" ceramic coated skillet W/O handle (aluminum pot grippers used) 6. Kifaru Gun Bearer rifle rest/holder 7. EB aluminum hiking poles Clothes: 1. Polar weight Cabelas poly long johns W/ zippered turtle neck 2. Norwegian wool sweater 3. Eddie Bauer First Ascent light down jacket & vest (worn separately or together while hiking, around camp or while sleeping.) 4. EMS GTX mountain parka 5. REI eVent rain/snow pants 6. Timberland 200 gm Thinsulate insulated boots 7. Cabela's GTX camo tall gaiters 8. LL Bean fleece billed cap W. ear flaps 9. LL Bean GTX insulated gloves & spare fleece liners 10. Heavy wool "sleeping sox" Both sleeping pads go in a stuff sack and are strapped to the bottom of the pack. (The EXOS comes with these bottom straps.) The last time I had essentially the same gear in my Terraplane pack which weighs 7 1/2 lbs.!