Here is how to install the Viper PDW Stock from Strike Industries. This might need some modifications of installing  on airsoft guns... "The Strike Industries Viper PDW stock represents the pinnacle of ultra compact PDW systems. At the compressed position, the compact Viper PDW allows for effortless maneuverability particularly in close quarters and vehicular operations. With the press of a button, the rapid deployment system instantly springs to the extended position for greater shot stability. Previous PDW systems for ARs have been notorious for expensive proprietary systems, spotty reliability, and poor ergonomics."