Shimano's Alivio Rear Derailleur is built to withstand the rigors of off-road riding, with a lightweight aluminum body and low-friction pivots for incredibly easy and smooth shifting. And, the Alivio features 11-tooth pulleys, which alternate chain-link contact reducing wear and smoothing pedaling.
An important part of a rear derailleur's job is keeping the chain taut as you change gears. Chain-wrap capacity is a number that tells whether or not a derailleur will be able to do this on the drivetrain you plan to use it on. Calculate chain-wrap capacity with this formula: Chain-wrap capacity = (large chainring - small chainring) + (large rear cog - small rear cog). Example: 44/29 chainrings and a 11-28 cassette: (44 - 29 = 15) + (28 - 11 = 17) = 32-tooth chain-wrap capacity.