Another ASMR session with 4UAD Smart Airsoft with an upgraded CYMA MP5K. The process of upgrading the MP5K airsoft gun in this session involves several steps. First, the gun is taken apart and the gearbox is removed. Next, the sensor is tested and the wire is trimmed to fit the gearbox. Then, the sensor is double checked and the gears are shimmed to ensure smooth operation. After that, the piston is installed and the gearbox is closed. Finally, the stock is installed and the gun is ready for a final test and a mag dump.