Progressive AEG spring - M150

SLONG Airsoft

is an airsoft manufacturer in Taiwan producing spare, upgrade parts and accessories such as hop-up chambers, inner barrels, motors, connectors, wiring, parts for gearbox and even outer parts such as handguards and stocks, so you can make a complete AEG just using parts from them. In 2020 SLONG Airsoft released its own M4 AEG rifle.