Clarence Lai, the Airsoft Surgeon, and who runs the Bang Bang Big Boys Toys in Central, Hong Kong, shows Gas Blowback Rifles for the month of April 2019. These are mainly gas blowback from Umarex, so watch the video to find out what these are... "Clarence Lai AKA Airsoft Surgeon gives us a quick run down of the most popular GBB for your games."