This Back-to-Back Bow-TieShower Door Knob is constructed of solid brass and is designed with a concave gripping surface that provides a comfortable feel when opening or closing the shower door. Each side of the knob measures 1-1/2 inches (38 millimeters) in length, and has a 1-1/4 inch (32 millimeter) diameter. This shower door knob requires a 3/8 or 1/2 inch (10 or 12 millimeter) diameter hole for installation. It is used by several shower door manufacturers.