Lion Gears Easily and Quickly Mounts on Rifle's Existing Swivel Stud Innovative Design Makes it Mounts on the Swivel Stud Much More Stable than Regular Swivel Stud Adaptor Low Profile Picatinny/Weaver Mounting Deck With 3 Slots Adjustable Rail-Levelness Provides Up to 10 degree Andle Compensation in order to keep the Rail Surface as Much as Parallel to Barrel