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.