This Shimano Tourney 78 Speed Rear Derailleur has a double servopantograph technology that improves adjustability and resists weather and contamination The guide pulley tracks the cogs closely while moving front to back optimizing each shift It has a shorter derailleur Smart Cage that grants you MegaRange capability with the shorter cage Features Model No RDTX800 Series TOURNEY TX Rear speeds 87 Compatible chain HG 876speed Max front difference 20T Low sprocket Max34T Min28T Top sprocket Max14T Min11T

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