Ruger manufacturers designed this magazine for the Ruger Mark IV 22/45 semi-automatic pistol.
The maximum capacity for this magazine is (10) rounds. Will only hold .22 Long Rifle caliber rounds. Constructed of a strong steel housing to perform well in harsh environments, and given a blued finish to avoid corrosion and wear, embedded with a hi-tensile compression spring to assure a smooth transition between magazine and chamber.
Ruger produces bolt-action, semi-automatic, and single-shot rifles, shotguns, semi-automatic pistols, and single and double action revolvers. According to the ATF statistics for 2015, Ruger is currently America's largest firearm manufacturer, as well as the second largest pistol/revolver manufacturer (behind Smith & Wesson) and rifle manufacturer (behind Remington) in the USA.
Note: This magazine will only work with the 22/45, if you have a standard Mark IV, or any other Mark IV that is not the 22/45 this magazine will not work!