The G&G AEG Power Spring is made for most-all Airsoft metal gearbox AEGs. Constructed of tempered high-carbon steel wire with a variable pitch, it is one of the best ways to adjust the FPS output of your metal gearbox AEG. The G&G AEG Power Springs are high quality, high strength springs that are built to last and maintain their tension. This is a perfect spring for any AEG, dramatically increasing the FPS from the standard stock spring. It is highly recommended when installing an upgraded spring to also install an upgraded metal ball bearing spring guide and metal bushings.