Our take: This JBU M150 Airsoft upgrade spring is made for most-all airsoft metal gearbox AEGs. Constructed of oil-temper steel wire with an irregular pitch, it is one of the best ways to adjust the FPS output of your metal gearbox AEG. High quality, low price tag. Get more power out of your AEG today! FPS rating: 420-450 FPS Disclaimer: Any and all airsoft upgrade parts purchased from Airsoft Megastore will be used/installed at owner"s discretion. We are not responsible for any damage that may occur. For best results, please have a professional airsoft Tech install all upgrade components at a certified professional airsoft technician/shop.