That's for my SSD in the optical bay. 2011 MBP. Purchased near release date. I think Apple released a EFI update enabling the 2nd SATA port to do SATA 3 / 6 Gbit/s
Here's more info about the SATA II vs SATA III
http://blog.macsales.com/10433-macbook-pro-2011-models-and-sata-3-0-6-0gbs-update-5272011
MBP13 2011 on release has a SATA II optibay, which is what I have. The difference between SATA II and SATA III is physical, so a software update isn't gonnna change it. The EFI update was to fix issues with the connector I believe.
If you buy a MBP today, I believe all of them will have SATA III.
