Cactus Jack Field Expanding Backpack has a main compartment that is 19 x 13" and it expands from 5" to 10" to accommodate extra gear.
Main area expands from 5" to 10" to fit more gear
o 2 accessory pockets
o Water bottle mesh pocket
o 2 electronics pockets on shoulder straps
o Removable waist belt
o Daisy chain holds rain gear, etc.
o Up to 2,470-cu. in. capacity, 40.48-liter capacity
o Color O.D. Green, Tan