FEATURES:PSEM airsoft AEG steel gear set with piston.Replace Maruis original gears with this upgrade steel power gear.Package with Hi Speed Flat Gear set plus full-teeth piston.Full teeth piston is made of reinforced plastic and the first seven teeth are made of metal.Gear set is the substantial high-cost performance gear set.Torque up gear is designed to increase torque for pushing higher spring tension in power upgrade AEG.Suitable for Element, Systema, Laylax & Tokyo Marui Airsoft AEG piston series.As always, upgrading AEG require neces