Bracket to hold surplus 127 mm (5 inch) 8-diopter biconvex glass lens upright. Two versions: the one with ribs on the base support has less material, so should print faster. The lens is AllElectronics # LNS-65 http://www.allelectronics.com/make-a-store/item/lns-65/8-diopter-lens/1.htmlThis lens is heavy and not of great optical quality (as you can guess from the price) but OK for classroom optics demo. OpenSCAD files for lens holder are included.