Like Shimano's pro-level offering Dura-ace 9000, the new Ultegra 6800 Compact 50/34T crankset uses the new 4-bolt spider which is compatible with compact rings or big rings--together with the lightweight tubular aluminum design and super stiff Hollowtech II spindle, this crankset is a great way to go race-level 11-speed, shave some weight, and not break the bank.
4-bolt spider BCD is the same for all ring sizes so if you want to try pushing a bigger ring, you can
Lightweight tubular aluminum design is responsive and ultra strong
Hollowtech II spindle construction adds stiffness for better output
50/34 chainrings gives limitless gearing options for all riding situations