This Colt M4 CQB-R is a gas operating rifle with full Colt trademarks (licenced from Cybergun) engraved on the metal receiver. This GBB package comes with a 50 rounds gas magazine, a foregrip, and a BB loader. Green gas is recommended to be used on this GBB. There are two valve blockers included in this King Arms gas blowback rifle package, which one of them is already installed in the rifle. To adjust the power, user can just switch between the higher or lower power valve blocker. To adjust the Rate of Fire for this rifle, users can use the four different sizes pink color speed buffers to achieve what they prefer. The thickest and thinnest speed buffers have been installed in the stock tube. By adding another speed buffer to reduce the travel distance for the recoil spring, higher ROF can be achieved.