Umarex Hammer owners want the most from their .50 caliber Hammer and this patented dual chamber mag provides more. This newly designed magazine is engineered to utilize the airflow released behind each slug. As the air travels behind the slug and through the magazine, it pushes the internal chamber seals both forward and backward creating a seal against both sides of the magwell. This patented sealing method means less air loss, a pick up of up to 25 feet per second in performance and nearly eliminates any air escape from the sides of the magwell. This magazine is backward compatible with the original Hammer and is included with the currently shipping Hammer .50 and the .50 caliber Hammer Carbine.