Shimano deore m591 9 speed rear derailleurif youre looking for high performance mountain bike mtb component for having fun on the trails without worrying about durability, the deore m591 9 speed rear derailleur is an excellent choice'. '.strtoupper('c')ompatible with both 8 and 9 speed drivetrains, shimano has built this rear mechanism from durable alloy and steel, so it can withstand the toughest trails and the harshest terrain.features material alloy and steel construction leads to lower weight without compromising strength and durability speed 8 9 speed cage length long cage mount type standard hanger mount clutch option no compatibility 8 9 speed mtb cassettes and shimano 8 9 speed mtb drivetrains wide link design increases rigidity and service life top normal return spring lends to incredibly intuitive operation when combined with rapidfire shifters large 11 tooth pulleys are used for longer life two fluorine coated link bushings for low friction operation compatible with 28 34t low sprocket weight 299g approx.a 2 year warranty is offered with all shimano products from chain reaction cycles 3 years on dura ace and xtr products.buy shimano components from chain reaction cycles, the world's largest online bike store.