A quick overview from Laylax on the Picatinny Rear Stock Base for Tokyo Marui GBB MP7A1 under the First Factory brand with versions available for the AEG version as well... "Customize the stock of your Tokyo Marui MP7 A1 gas blowback machine gun! Learn how to install LayLax's new Picatinny Rear Stock Base, which allows you to mount a rail-compatible stock."