Rail type: Picatinny. Machined from: Solid 7075 T6 Aircraft Grade Aluminum Top Mount Finish: Matte Black Hard Coat. Bottom assembly machined from: 4140 steel Bottom finish: blue. Finish: Matte Black Center Expansion: 4.1" Overall Bracket Length: 5.094" Height: 0.35" (Top of Receiver to Top of Picatinny) Weight: 2.5 oz Quick Detach Ring Compatible: Yes. Ambidextrous: Yes. Compatible with Picatinny or Weaver Scope Rings. Mounting Tools: 8-32 Hex Socket Head Screws and Wrench. Supplied Torque Specs: 20 in/lbs Our Mosin Nagant mount allows you to remove the rear blade sight and install our base without the need to desolder anything. the most stable bases on the market and uses the rear sight housing, so there are no major modifications to your rifle as with other brands Installation: Remove the sight from the rear blade of the housing. Keep the original pin as you will need this to install our base.Insert the tabbed side of our steel base into the back of the rear sight. Check the fit on the front of the steel base. The corners and front may need to be filed down to achieve the optimal fit. Once the base sits fully on the rear housing, insert the retaining pin from the original view. Adjust the set screw to take up any play in the rail. Screw the aluminum top bracket to the steel base. This support can be placed in any direction. We recommend: 0 MOA - if you shoot from 0 to 450 meters. 20 MOA – if you shoot 500-1000 yards.