The shimano alivio t4000 9 speed rear derailleur a great value alivio rear derailleur offering crisp performance on and off road for 9 speed drivetrains shimano alivio t4000 9 speed rear derailleur features wide link design increases rigidity and service life alloy body and outer link leads to lower weight without compromising strength and durability 11 tooth pulleys for reduced pulley wear and chain noise advanced light action design with low friction fluorine coated link pivot