This vintage style glass door knob set is constructed of clear fluted glass and brass plated materials. This knob set is designed for indoor use only, and it fits door panels from 1 in. to 1-3/4 in. thick. The diecast base on these knobs include the set screws for fastening the knobs to the 17/64 in. x 3-1/2 in. square steel spindle with 3/8 in. -20 threads. Note: This passage door set cannot be used on pre-bored doors that have large newer style door knob holes without first prepping them to receive this hardware. Installation tip #1: Because the fasteners of the rosettes require a solid surface to mount to, the large 2-1/8 in. (approximate size) holes must first be filled with a hardening filler, to then be able to receive the rosette fasteners. Products like Fix-It-All® and Bondo Body Filler® have worked well for some, but care must be used to avoid damaging any prefinished door surfaces during application and finishing. Installation tip #2: Apply a small amount of Loctite ThreadLocker 271® to the set screw threads in the event they are loosening Loctite® purchased separately.