A.
anwered by: canteau
This chainring is not designed to be used with 10-speed chains and does not include shift ramps or pins. You might be able to get it to fit on your Shimano Ultegra 6600 cranks but shifting might not be ideal. If you are replacing a worn chainring the Shimano 6600 39t chainring is available here:
http://www.treefortbikes.com/product/333222348036/324/Shimano-Ultegra-FC-6600.html