Mesa Tactical Saddle Rails constructed from 6061-T6 The 91680 Rail wraps around the top of the shotgun receiver. The factory trigger pins are replaced by an internally threaded steel pin (in the rear) and paired Chicago screws (up front), to which both sides of the saddle rail are securely bolted. The saddle rail is Type III anodized for a rugged surface finish. This Saddle Rail is specially contoured to allow operation of a semi-automatic bolt on the right side of the receiver, so it can be installed on Remington 1100 and Remington 11-87 semi-auto shotguns as well as Remington 870 pump shotguns. The rail is notched at the rear to accommodate Scattergun/Wilson style ghost ring sights, and extends to the front of the shotgun receiver (5 inch rail), 2 3/4 inches past the front of the receiver (8 1/2 inch rail), or just beyond the barrel’s magazine lug (20 inch rail). No fitting or gunsmithing is required to install.(Firearm NOT Included)