Plenty of manufacturers have proven that polymer AR-15 magazines are durable enough to stand up to combat use, and today's AR owners have taken to polymer magazines as an affordable, durable go-to for their rifles. This AR-15 Polymer Magazine is constructed using durable DuPont Zytel polymer, which has been proven to perform. Each polymer AR-15 magazine is designed for use with .223 Rem. and 5.56 NATO cartridges only and features a 30-round capacity with a heat-treated chrome-silicon wire serving as a dependable magazine spring. The spring is topped with an injection-molded follower that's designed to provide reliable feeding in your standard AR platform.