We get more information on the RA-Tech Challenge DIY Pack for the GHK M4 Gas Blowback Rifle as RA-Tech sent in video link on Christmas Day. For those who think they are competent enough to build their own upgraded M4 Gas Blowback, then this kit can be something to order for a project. Another video they provided is about the RA Desert Storm Steel Slide & Outer Barrel for WE G17.