The new PMX AR 30 Round Magazines features the THRiL polymer-matrix (PMX) construction, designed for high-performance and extreme durability. The PMX technology combines impact-resistant polymer and an elastomeric strike plate to ensure maximum performance in all situations.THRiL's New 30 round AR Mag for AR15s chambered in 5.56/.223 Remington. Polymer matrix construction Ergonomic design Elastomeric strike plate Anti-tilt follower Stainless steel spring