Accurate-Mag AICS Pattern Single Stack Magazine 338 Lapua Mag 5 Round 3.850" Length. This Accurate-Mag magazine is made from a strong steel heat treated for the best durability and carries a black Teflon finish for increased mag longevity. The magazine is designed to fit the Accuracy International Chassis System (AICS). This magazine fits the .338 Lapua Magnum round in a single-stack single-feed configuration with a 5 round capacity.