The vk-1 uses a patented low-profile piston system design featuring optimum gas port sizing and an advanced piston assembly.This features a unique cup and spigot design that improves the gas seal and overall efficiency of the gas system.The vk-1 includes a staged gas bleed system that allows the rifle to operate consistently, either suppressed or unsuppressed, with varying types of factory ammo.The vk-1 short stroke piston system includes a fully-supported one-piece op rod and removable gas block which matches the footprint and weight of a standard di ar-15 while providing the benefits of a piston driven system.Caliber: 5.56mmBarrel Length: 10.50"Capacity: 30+1Grips: Black Magpul K2Sights: None, OpticReadyWeight: 6 lbsStock Material: SyntheticOal: 27.30"-29.90"Stock Finish: BlackBarrel Length Range: 10" to 10.99"Weight Range: 6 lbs to 6.99 lbs