SRM Arms Inc. SRM 12 Gauge 16 Round Shotgun Magazine Black. It fits the SRM 1216 and provides unsurpassed firepower" force multiplication" and tactical advantages. Specifications for SRM Arms Inc. SRM M1216 12 Gauge 16 Round Shotgun Magazine: Manufacturer: SRM Arms Inc. Magazine Capacity: 16 Round Caliber: 12 Gauge 16-Round Capacity Package Contents: SRM Arms Inc. SRM M1216 12 Gauge 16 Round Shotgun Magazine SRM Arms Inc. SRM1216MSB-16RD: SRM M1216 12 Gauge 16 Round Shotgun Magazine Black