Machined from one solid piece of steel. Designed for use with dove Lyman 57's and 66's hug the receiver. Provide the lowest line of sight and the least protrusion. Audible click, 1/4 minute adjustments for windage and elevation. Elevation slide in 3 minute increments. Quick-release button. Stop for return to zero. 57 series for round receiver rifles, 66 series for flat receiver rifles.