Rugged and lightweight, aluminum shell holders put extra 12 gauge shotshells on the left side of the receiver for fast tactical reloads. Shells are held in place with a unique, internal Santoprene(TM) elastomer rib that securely retains even heavy slug shells during vigorous movement or heavy recoil. Available in sidemount (SM) or Picatinny rail (PR) configurations. All necessary installation hardware, tools, and instructions included. Remington Sidemount is available in 4-, 6-, and 8-round capacities and uses steel-on-steel, threaded adapters that replace the trigger group pins to anchor the shell holder securely to the receiver. Remington 870 shotguns re Mfg: Mesa Tactical Products SPECS: 6061 T6 aluminum, anodized, matte black. For 12 gauge only. All models include mounting hardware, rubber gasket, and installation instructions. Right Hand models only. Remington Sidemount fits models 870/1100/11-87 (may require modification to gun). Rem 4-Round Sidemount - 5A 1/4&