Monstrum Picatinny Side Saddle Ammo Holder .410 Gauge/.243 Winchester/.308 Winchester/7mm-08 Remington Black. Available in different versions for different diameter cartridges: For .223 Remington/5.56 NATO For .243 Winchester/.308 Winchester/7mm-08 Remington. For 12 gauge shotgun shells. Not compatible with other calibers. Unit installs to your picatinny mounting platform with no additional gunsmithing required. The low profile design does not interfere with the mounting of rings or optics. Specifications for Monstrum Picatinny Side Saddle Ammo Holder: Manufacturer: Monstrum Color: Black Features of Monstrum Picatinny Side Saddle Ammo Holder Picatinny Side Saddle Ammo Holder for .410 gauge/.243 Winchester/.308 Winchester/7mm-08 Remington. Not compatible with other rifle calibers. Accommodates 4 spare cartridges. Installs on to your picatinny mounting platform with no additional gunsmithing required. Low profile design does not interfere with the mounting of rings or optics. Package Contents: Monstrum Picatinny Side Saddle Ammo Holder Monstrum ZH137: Picatinny Side Saddle Ammo Holder .410 Gauge/.243 Winchester/.308 Winchester/7mm-08 Remington Black