There are 4 different GBB MP7s on the market, namely by TM, VFC, KWA and WE. None of them have compatible magazines, and you must order the adapter made for your gun. Notably, Umarex have rebranded both VFC and KWA MP7s so take particular care in identifying which gun you have (hint: if it doesnt work, its probably the KWA one, if it almost looks like an MP7, its the WE, and if it brings a proud tear to your eye when using it, its the TM)