Originally Posted by
Eclectus
There was a difference between S-Works SL2 Tarmac frame and Pro, but in 2009, S-Works Tarmac went to SL3, so Pro got the old SL2 frame. In other words, when S-Works went from SL frame to SL2, the Pro model got the SL frame, and similarly when S-Works then went to SL3, the Pro frame got SL2.
The Pro for 2009 and 2010 uses the SL2 design/molds, but is not made of the same level of material as the s-works SL2 was. Similarly, the 2011 Pro uses the SL3 design/molds, but still uses the lower level of material.