This new Glock 34 Gen 4 MOS pistol fires the 9mm round. It has a 5.25" barrel with an overall black finish. This semi-auto pistol has an under barrel rail, a weight reducing slide cut out, an extended slide release, and the MOS adapter kit. This MOS (Modular Optic System) allows the shooter to mount the sight of their choice using one of the 4 adapter plates. The adapter plates are for: 1) Eotech/Doctor/Insight/Meopta 2)Trijicon RMR 3)C-More 4)Leupold Delta Point. Currently on the gun is the cover plate. This pistol also comes with 4 backstraps, a magazine loader, a bore brush & rod, lock, hard case, and three 17 round magazines.