An improved magazine for use in existing firearms comprises a housing, a follower, a spring, a spring hold and a cap. The housing comprises protruded surfaces for structural strength and a projection that acts as a stop member to define the maximum insertion of the magazine into the firearm magazine well. The follower comprises two follower legs and a spring retainer, and travels up and down the housing. The perimeters of the follower and follower legs mirror the internal profile of the magazine housing for a well-defined travel path within the magazine housing. The spring hold comprises a spring retainer and a round protrusion that locks it into the cap via a circular cut. The cap comprises flanges that slide into the slots against the end stop at the bottom of the housing.