The Glock 21 V MOS delivers serious .45 ACP stopping power with factory optic-ready capability in a full-size platform. MOS mounting system, refined ergonomics, and legendary Glock reliability combine with the proven .45 ACP cartridge to create a versatile pistol for duty, home defense, and tactical applications. The MOS (Modular Optic System) slide is precision-machined to provide a mounting system for popular red dot optic sights. The pistol includes one adapter plate to get you started, and additional adapter plates (sold separately) allow you to quickly and easily mount miniature red dot sights for faster target acquisition and more precise shot placement. The MOS system allows you to mount your preferred optic without the need for custom slide milling, maintaining the factory warranty and structural integrity of the slide. The 4.61" Glock Marksman Barrel features enhanced rifling that delivers improved accuracy over previous generation barrels. The full-size frame and longer barrel provide excellent recoil control for the .45 ACP cartridge while maximizing velocity and delivering the proven stopping power that has made .45 ACP a trusted choice for decades. The SAFE ACTION System provides three independent mechanical safeties that disengage sequentially as the trigger is pulled and automatically re-engage when released-total reliability with no external levers to snag or forget. .45 ACP with 10+1 capacity 4.61" Glock Marksman Barrel Enhanced rifling for improved accuracy MOS optic-ready system Precision-machined slide for red dot mounting Includes one adapter plate Accepts popular miniature red dot sights (additional adapter plates sold separately) Front serrations for press checks Ambidextrous slide stop levers Flared magwell for faster reloads No finger grooves for universal fit Reversible magazine catch Matte black finish SAFE ACTION System with three independent safeties Full-size frame for maximum control Includes (3) 10-round magazines