Firefield AR 30mm Fixed Mount Cantilever Black. As a cantilever mount this unit is designed to be used with rifles with high recoil cartridges since they provide extra clearance between the shooter's eye and the rear of the scope allowing for a comfortable and safe eye relief distance. By extending the scope forward over the rifle's action the Firefield 30mm fixed mount may help shooters achieve better balance and a more natural shooting position. This is good for scopes with large objective lenses. Specifications for Firefield AR 30mm Fixed Mount: Manufacturer: Firefield Gun Rail: Picatinny Fabric/Material: 6061-T6 Aluminum Color: Black Tube Diameter: 30 mm Weight: 4.9 oz Dimensions: 5.132x2.034x2.515 in Gun Type: Rifle Finish: Matte Features of Firefield AR 30mm Fixed Mount 47mm/1.85in forward offset Fixed mount design Fits 30mm riflescope tubes Package Contents: Firefield AR 30mm Fixed Mount Rubber Lens Cover 1In. Scope Mounts Lens Cloth Manual Firefield FF34011: AR 30mm Fixed Mount Cantilever Black