The AC22037 34mm Colt Knob Mount is designed for 34mm riflescopes. It features colt-style thumbscrews which easily and securely attach to MIL-STD-1913 Picatinny rails.This mount is adjustable for eye relief. The scope rings can be placed in four locations along the base. Simply remove the base screws, move the rings to the desired location, and re-install the mount screws.