Thank you for your inquiry regarding this item from Prime-Line Products. If the doors have large pre-drilled holes to receive regular door knobs, the mounting screws of the rosettes will not have any wood to screw into as required for installation. However, that does not mean that the installation of these glass knobs in pre-drilled doors is impossible, only that the door knob holes will need to be filled prior to installation of the knobs.
The square metal spindles of these glass knobs require only a 3/4 inch hole for installation, so you'll want to find a hardening-filler that will serve this purpose. Kindly see the suggested simple method of preparation for installation as attached below. Keep filler off finished surfaces of door panel (both sides) as some sanding and/or finishing may be necessary.
You may also consider item no. E-2317 available for order from within this same site which includes the 2 glass handles, spindle, rosettes, and a mortise latch bolt. It comes complete with fasteners for a quick and easy installation.
For additional questions regarding this item, or any other product manufactured by Prime-Line Products, please call their toll free number at (877) 649-9740, or contact them by email at email@example.com