CNC machined for precise tolerances, this ring system provides repeatability and flexibility by allowing you to remove and replace your scope with the confidence it will return to zero. Great when traveling and when venturing out on that once in a lifetime hunt, you can carry a spare scope already sighted in and ready to go as a back-up! Works only with Talley bases. Notes:Rings lock with a torx head screw instead of a leverMounting hardware included Ring Height Selection (per Talley):Low for scopes up to 44mm objective with standard barrel contourMedium for scopes up to 50mm objective with standard barrel contourHigh for scopes with a 56mm objective with standard barrel contourExtra-High for large objective scopes with heavy contour barrels