Attaches in place of the stock top strap on most Buck Mark pistols. Current versions of this base use the Picatinny style rail slots and spacing. This style base is not compatible with the proprietary Browning rings. *IMPORTANT: Some earlier versions of this rail were sold using the Weaver-style configuration of slots and spacing. Before purchasing, check the packaging to confirm that the sight you have fits the base on your firearm. The general rule is that Weaver-style devices will fit on Picatinny-style rails, but Picatinny-style devices will not always fit on Weaver-style rails.