These are involute herringbone pattern gears for Wade's Most Excellent Extruder. The gears that came in my Printrbot Plus kit were warped and misshapen. Laser-sintered nylon is a very precise way to make objects, why not my extruder gears?
See the picture with the black and the white gears:
The Black gear came with my Printrbot Plus kit.
The STL file shows a diameter of 63.78 mm.
The gear that was printed by a Printrbot in my kit measures 61.25 (averaged 8 measurements)
The white gear was printed by Shapeways in Laser-sintered nylon and averages 63.25 mm
If you want a little Headhunter - Gothic - Cannibal - Biker vibe on your 3D Printer, check out the Skulltruder!