The ProMag PM017 magazine loader was originally designed to load the (100) Round .223 / 5.56 BETA magazine. The loader is slipped over any AR-15 / M16 .223 / 5.56 type magazine. Five cartridges are dropped in and loaded by depressing the plunger. The process is repeated until the magazine is loaded. Manufactured from injection molded, glass filled black Mil-Spec polymer construction.