Includes Lock Plate. The Plus-2 Adapter is a replacement set of hollow butt-plate and inner base to further raise the capacity of the Optimum Mec-Gar magazines including: MGPB9218AFC, MGPB9613AFC, MGCZ7517AFC, MGCZ4012AFC, MGP22618AFC, MGP2264013AFC, MGPT9218AFC and MGPT4013AFC. The "Plus-2" Adapter will not work on other magazines.