GLOCK OEM Magazine Extension Insert, 9MM, 40S&W & 357 SIG, Black, Not G43, Must Purchase OEM Plus Two Magazine Extension (GLSP07151) Separately, Packaged 50976 This Glock Factory Magazine Extension Insert is a factory original from Glock. Factory replacement parts are manufactured to the exact same specifications and tolerances and use the same manufacturing materials as the original parts which guarantees excellent fit and reliable operation.