Excellent Used Condition Have only used for a couple of weekend trips. I believe this is the 40L model From Topo Designs: Features and Specs: Built with recycled nylons Carry-on compliant 3-way carry (backpack straps, shoulder strap and grab handles) Foam structure with padded recycled ballistic nylon back panel U-shape entry to large main compartment Internal mesh organization pockets U-shape entry to secondary organization compartment Larger zippered security pocket and dual slip pockets Vertical exterior zippered pocket with dual security pockets Easy access to back panel laptop compartment, fits most 15” laptops Stowable contoured padded spacer mesh shoulder straps Load-lifter straps and sternum strap Removable adjustable padded shoulder strap Expandable side water bottle pockets Vertical daisy chain webbing Heavy-duty YKK zippers with security loop on main compartment PackFast™ Attachment Clips for attaching smaller bags Signature high visibility recycled yellow pack cloth interior, recycled black pack cloth interior on black color only Meets most airline carry-on requirements Materials: 1000D recycled nylon, 400D recycled nylon, 210D recycled nylon, 1680D recycled ballistic nylon Dimensions: 14"w x 22.5"h x 7.5"d Volume: 2441 cu. in. / 40 L (*can expand to 45 L when fully packed) Weight: 58.4oz