The Glock 21 Gen4 is the full-size .45 ACP Glock in fourth-generation specification, featuring interchangeable backstraps, dual recoil spring, and ambidextrous magazine release. The G21 has been the primary Glock .45 ACP offering since 1990 and competes directly with the SIG P220 and HK45 in the full-size .45 duty market. 13-round capacity gives it the highest .45 ACP factory capacity of any production service pistol. Type: Pistol Action: Striker-Fired Caliber: .45 ACP Capacity: 13 Year introduced: 2010, Austria Weight: 29.28 oz Overall length: 8.22" Status: Active Intended use: duty, carry