Upper and lower Ring Portions Precision machined from one solid block of steel to strict tolerances for optimal fit. Heat treated QPQ Nitride Matte Black Finish for strength and added weather and wear resistance. Progressively machined for a precise inner ring diameter to achieve optimal tube alignment; Inner surface with groove cuts to guarantee tube retention even under high recoil. Radiused edges and corner to prevent snagging, scratching or tearing of other gear and for effortless access to scope windage and elevation turrets