This project is part of a collection on open source optics meant to radically reduce the cost of experimental optical equipment.
This is a parametric chopper wheel - so you can choose how many holes, their sizes, and the overall size of the wheel to customize them for your own optical experiments.
The default code has an m3 nut cage to firmly affix the wheel to a spinning shaft.
The OpenSCAD and STL files of some examples are here: http://www.thingiverse.com/thing:28121
See: Zhang C, Anzalone NC, Faria RP, Pearce JM (2013) Open-Source 3D-Printable Optics Equipment. PLoS ONE 8(3): e59840. doi:10.1371/journal.pone.0059840 open access