Here's the detail as from the factory website
MaxPedition Devildog Versipack. The Maxpedition™ DevilDog™ (#0405) is a spacious buttpack equipped with pouches on both side for carrying 1L Nalgene bottles. Padded belt strap with 2” quick release can be concealed inside. Main compartment opens to reveal 500 cu. in. of space with heavy duty internal organizers in front and back of the compartment, drains through bottom grommet. An internal snap retains keys or a pair of gloves. Compression straps integrate into a carry handle. The DevilDog Versipack comes with an additional adjustable 1.5” shoulder strap with removable shoulder pad. Nylon attachment points in front and on the side allow modular attachment of more Maxpedition accessories. Breathable sandwich backing allow comfortable wear during extended periods of activity.
Dimensions: Frontal: 7 in x 5 in x 1 in with internal divider, Main: 11 in x 9 in x 5 in with internal organizer, Belt: Padded 2 in adjustable waistbelt; 60 in max. waist size, Carry: Handle or 1.5 in shoulder strap with non-slip pad.