Shimano's Deore LX 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 LX features 11-tooth pulleys, which alternate chain-link contact reducing wear and smoothing pedaling.
Largest cog this derailleur can handle: 34 tooth
Weight: 311 grams
Low Normal means that the derailleur spring assists shifts to the larger cassette cogs, which speeds and smoothes shifts and greatly reduces the chances of damaging the derailleur during upshifts because you can't force it with the shift levers.