The Shimano 105 5800 11-speed rear derailleur has an entirely new design. The long cage version can handle up to 32T cassettes, making a triple redundant.
The Shimano 105 5800 Group offers many new technological improvements just like in the Ultegra 6800 group. Every part has been given a new twist.
The quality difference between Shimano's Dura Ace, Ultegra, and 105 has never been so small. If you're interested in an excellent price / performance ratio, this is the perfect component group for you: a no-nonsense, reliable, durable, and high-performance group with an attractive design.