The ProMag® .45 ACP 13-Round Magazine for Glock® 21 Pistols is an affordable alternative to expensive factory Glock magazines, faithfully manufactured to tight specifications for consistent, reliable operation with your favorite Glock pistol. This magazine features a durable, high-impact DuPont™ Zytel® polymer body with a full-length steel lining for superior durability and lasting performance in fast-action defensive environments. Numbered witness holes offer quick, visual round counts, while precise tolerances deliver a snug, wobble-free fit for superior reliability and dependable feeding performance. Plus, the high-tensile chrome silicon spring, coupled with a non-tilt polymer follower, ensures proper cartridge alignment and jam-free operation. Better yet, this centerfire pistol magazine is backed by a ProMag lifetime warranty for lasting service you can truly depend on. What are you waiting for? Order now!