Main compartment dimensions: 18'' H x 12'' W x 6.5'' D, Center compartment 18'' H x 12'' W x 2.5'' D. Top Outside Compartment: 5'' H x 10.25'' W x 1.25'' D, Bottom Outside Compartment: 10.75''H x 10.75''W x 1.75'' D. These compartments have internal mesh pockets, zippered pockets, dividers with hook and look fasteners, and keychain hook. MOLLE compatible PAL webbing on the front & bottom pockets, shoulder straps, and the sides of the backpack. Heavy Duty Lockable Zippers on ALL of the compartments to keep your valuables secure.