07 S2R1k rear brake cylinder

[FastAndLight]

My rear brakes used to do something.  Then they stopped.  I asked the shop doing the 6k maintenance to look into it.  The tech bled the lines, adjusted the linkage, and got me a little more use, but not much.  He said (and research here has confirmed) that the cylinders go bad pretty quickly.  I was going to pick up a new one from here:
http://www.yoyodyneti.com/Category.aspx?CategoryID=3007
but I don't know which size I need.  I have a 2007 S2R1000. 

Thanks for the help.

[Howie]

PS11C, 11mm.