A screw-on filter for lenses with 49mm filters, designed to hold 40mm diameter (1mm thick) disks for creating bokeh effects.
The disks included in the Bokeh Masters Kit sold by DIY Photography on Amazon will fit (assuming they have not changed in size since I bought this kit in December 2014 - some of the disks will fit more tightly than others), or you can make your own through laser cutting, or just using scissors / razor blade / some other cutting device to cut your own out of card stock or construction paper.
I will create models for other thread filter sizes at request - email me at shapeways@illandril.net
I do not (yet) have bokeh disks to sell, but if I get enough requests I will.