The Rock Island Armory 45201 refers to the full-size A-1 1911 magazine that serves as a standard factory-produced replacement. Specifically designed for A-1 1911 models, this magazine can house 10 rounds of 9 mm ammunition. Constructed from steel, it adheres to the exacting standards of Armscor/Rock Island Armory, both in terms of specifications and tolerances. The manufacturing process and materials utilized are on par with those used in the production of original equipment magazines. The result is a flawless fit and seamless operation.