Shield Arms S15 +2 Magazine Extension, Mag Extension, Fits Shield Arms S15 Gen 2/3 Magazines, Aluminum Construction, Anodized Finish, Black SA-S15-S10-ME-2-BLK The Shield Arms S15 Magazine Extension adds 2 rounds to your S15 magazine. Shield Arm's unique" easy access floor plate design allows you to quickly access the spring and follower without having to remove the extension from the magazine body.