These KCI USA magazines are constructed from a proprietary polycarbonate formula, with a patented stainless steel internal feed lips, stainless steel increased power spring and an anti-tilt follower. The transparent opaque smoke mags feature dual round count markings to allow for visible round count confirmation from any side. The solid black mags feature a window, to allow for a round count. A textured outside surface ensures an intuitive grip for precise manipulations.