These combs fit the Bio-Rad vertical mini protein gels using the 0.75, 1.0, or 1.5 mm spacers. Bio-Rad doesn't sell 16-well combs, so they're useful when you have 15 samples and still want to load a molecular weight marker.
I printed these on a piece of blue painter's tape (to facilitate easy removal from the build platform) using a MakerBot Replicator 2. Using MakerWare software, I positioned the combs so that their wide flat side is down and printed using in PLA the default settings: medium quality, 10% infill, 0.2 mm layer height, 2 shells, and 230 degrees C.
UPDATE: The BioRad-advertised thicknesses of these combs is wrong. FOr instance, the 0.75-mm comb is actually only 0.6 mm thick, and that makes a big difference in performance. I've replaced the 0.75-mm file with a 0.6-mm file and the Sketchup file for modifications.