These are a custom labeled 308 BDC knob from the Leupold custom shop. They are calibrated for the typical 308 Match ammo shooting a Sierra Match King 168gr bullet at 2650 fps in standard atmospheric conditions at sea level. These knobs are a direct replacement for the factory knobs and are easily replaced by just removing the three set screws from the old knob, lift it, and put this knew one on the scope.
Manufacturer: Leupold Custom Shop
BDC Calibration: 308 168gr Sierra Match King @ 2650 fps
Scope: Any Leupold Mk AR scope with the P5 mil knobs. 3-9x40mm, 4-12x40mm, 6-18x40mm