The G21 Gen5 MOS delivers improved accuracy, light recoil the option to install an optic. Gen5 features flared mag-well has a larger funnel; Glock Marksman Barrel (GMB) more aggressive polygonal rifling with a target-style crown and tighter chamber specs; ambidextrous slide stop levers offer increased ergonomics for left-hand shooters and shooting with the support hand; removal of finger grooves; Safe Action System, safeties disengage sequentially as the trigger is pulled and automatically re-engage when the trigger is released; enlarged floor plate makes it easier to pull the magazine free of the pistol and customizable frame size with backstraps in two sizes with beavertail. The multiple backstrap frame allows the users to change the circumference of the grip to fit their individual hand size. MOS features a slide that is precision machined to provide a mounting system for popular optic sights. With multiple adapter plates (sold separately), you can quickly and easily mount miniature red dot sights. Includes one adapter plate, three magazines, mag loader, cleaning kit, pistol case and gun lock