This weight bag is designed to help counter-balance the weight of your ANVIS NVG mount. It reduces neck fatigue, which helps you stay alert during a mission. The bag is perfectly sized to fit on the 3" x 2" stock hook and loop on the back of HGU/56-P, IHADDS, and SPH-4 helmets, beneath the ANVIS battery pack. Constructed from 1000 denier water repellent Nylon Cordura. Dimensions Empty: 4.25" x 2.25" Dimensions Filled: 4" x 2" NOTE:Maximum size of prefilled weight for this weight bag is 14oz. Only the 10 and 14 ounce weights will fit into the NVG Counterweight Bag. Learn More