The SureFire high-capacity magazine for 5.56x45 mm (.223 Remington) ammunition, also available in a 100-round version, is compatible with M4/M16/AR-15 variants and other firearms that accept standard STANAG 4179 magazines. Constructed from Mil-Spec hard-anodized aluminum, they feed smoothly and reliably due to optimal geometry, non-binding coil springs, and ingenious nesting polymer followers. The long-lasting springs are cadmium coated for low friction and excellent corrosion resistance. Magazines require no lubricants and can be easily disassembled without tools for cleaning. SureFire High-Capacity magazines provide distinct tactical advantages: increased initial firepower in ambush situations; fewer reloads overall, which means less downtime and target distraction in a firefight; fast and easy magazine insertion, even with a closed bolt; less bulk compared to drum mags, enabling a normal weapon grip. The 60-round magazine—slightly thinner than two 30-round magazines clipped together and about the same overall length—fits in most dual magazine pouches, eliminating special carry pouches required for drum magazines.