How will you feel after spending all that time, money and energy building the perfect AR-15, only to have it stop running because of a poor-quality magazine? Feed your guns the right way by stocking up on these PMX 30-Round magazines. Designed for use in 5.56 NATO AR-15s, these all-new PMX 30-round magazines are built using an entirely new kind of construction method. PMX uses the THRiL polymer matrix, which enhances durability and ensures that these magazines will keep feeding rounds in any kind of situation. Inside each PMX 30-round AR-15 magazine, you'll find a long-lasting, stainless-steel spring that bottoms out on an elastomer strike plate. At the top of the spring is Mfg: Thril Inc.