Ruff's Precision Manufacturing Bravo Riflescope Cantilever Mount w/ Co-Linear Bubble Level 30mm 1.50 in FDE. Built in level is visible from the shooting position with the shooters' non-dominant eye for quick reference prior to the shot. Level significantly aids in accurate scope mounting by giving reference to the cant of the rifle during the scope mounting process while eliminating the need for multiple small levels and balancing acts Specifications for Ruff's Precision Manufacturing Bravo Riflescope Cantilever Mount: Manufacturer: Ruff's Precision Manufacturing Gun Rail: Picatinny Fabric/Material: 6061-T6 Aluminum Base/Mount Type: Cantilever Ring Mount Ring Height: 1.5 in Gun Model: AR-10 AR-15 Country of Origin: USA Features of Ruff's Precision Manufacturing Bravo Riflescope Cantilever Mount w/ Co-Linear Bubble Level Alignment lug to ensure cap/base alignment during cap screw installation Package Contents: Ruff's Precision Manufacturing Bravo Riflescope Cantilever Mount w/ Co-Linear Bubble Level Co-Linear Bubble Level What firearm models does the manufacturer say Ruff's Precision Manufacturing Bravo Riflescope Cantilever Mount is compatible with? The manufacturer suggests that Ruff's Precision Manufacturing Bravo Riflescope Cantilever Mount is compatible with AR-15 AR-10Ruff's Precision Manufacturing BC-30150-FDE: Bravo Riflescope Cantilever Mount w/ Co-Linear Bubble Level 30mm 1.50 in FDE