Since the development of the ultracentrifuge by Svedberg in the early 20th century, the separation of solutes with weak buoyancy differences has been feasible due to the enormous centripetal acceleration generated by such instruments. For high aspect ratio rods such as single wall carbon nanotubes (SWNTs), high speed centrifugation can be also exploited to yield length separation. Separation of order 10 milligram quantities into well resolved fractions in less than one day is demonstrated. The manner of the separation, properties of the resulting length fractions, and comparison of theoretical to actual results will be presented.