Monstrum Mossberg 12-Gauge Shotgun Side Saddle Shell Carrier Compatible with Picatinny Mounting Platforms Black. Built for use with shotguns equipped with a Picatinny mounting base the shell holder accommodates up to six 12 gauge shotgun shells. Unit installs on to your picatinny base with no additional gunsmithing required. Specifications for Monstrum Mossberg 12-Gauge Shotgun Side Saddle Shell Carrier: Manufacturer: Monstrum Color: Black Gun Make: Mossberg Gauge: 12 Features of Monstrum Mossberg 12-Gauge Shotgun Side Saddle Shell Carrier Side saddle shell holder for use with Mossberg 500/590/Shockwave/Maverick 88 Series shotgun platforms. Unit installs into the pin holes on the side of the receiver with no additional gunsmithing required. Accomodates up to six 12 gauge shotgun shells. Not compatible with other shotgun models. Package Contents: Monstrum Mossberg 12-Gauge Shotgun Side Saddle Shell Carrier Monstrum ZH133: Mossberg 12-Gauge Shotgun Side Saddle Shell Carrier Compatible with Picatinny Mounting Platforms Black