If your Shimano Dyna-Sys 10-speed mountain bike drivetrain features these specific rear derailleurs: M786, M781, M780, or M773, this genuine XT-level Derailleur Pulley Set is the proper replacement for your original equipment. This advanced grade pulley set has some specific features that work for the listed derailleurs and may not be an upgrade for other, unlisted models. First, you should know that Shimano has made a running change to the replacement set so that it works best with all listed models. In the original RD-M773 cage, both the 11T Guide and Tension pulleys were the same. This set has specific 11T Guide and Tension pulleys but works perfectly. The Guide pulley is the solid version, and is clearly labeled. The Tension pulley has cut outs, which offer improved mud shedding in this less protected zone. Follow the marked directional arrows at installation, as each unit is also directional. A close examination shows the bevels and shapes of the pulley teeth which are designed to engage the chain properly, offer retention and function, while reducing system friction.

Both pulleys feature great Shimano sealed cartridge bearings, which ensure long life, resistance to moisture and grime, and again reduce friction. Shimano does not provide any hardware for installation, as you are expected to the use the bolts that hold your existing pulleys in place. The POM composite material used for the wheels themselves is incredibly durable to long wear. You know you have put in some miles or live in a region with challenging conditions if you have to replace them often. You'll know it is time to replace them with the lower (Tension) pulley shows wear with a shark-fin type curve in the valley between each tooth. Even if you think the Guide (top) pulley looks like it has less wear, we highly recommend you replace the pair at the same time. Ideally this is accompanied by a chain and cassette change as well, so you can usually plan ahead to do these basic services all at once.