Shimano xt m781 shadow 10 speed rear mechefficiency was the key principle when designing the shimano dyna sys xt m781 gs 10 speed rear derailleur the derailleur was designed with a longer swing arm and a tighter spring for crisper shifting when you want it and less ghost shifting when you dont the dyna sys rear derailleur will stay in adjustment longer and deliver consistent performance with each ride featuresdeore xt shadow dyna sys 10 speed rear derailleur delivers reliable and precise s