The Tamrac M.A.S. Flash Accessory Pocket - 1.7 (Black) is a fast-access pocket for flashes like Canon's 580EX II, Nikon's SB900, light meters, or other similarly sized flash units. Simple front pocket for additional small essentials. Quickly attaches to our Arc? compatible products or to any belt. M.A.S. (Modular Accessory System) compatible - This system allows photographers to customize and personalize their backpacks, shoulder bags and cases by using accessories that quickly attach to the M.A.S attachment slots.