The Shimano Alivio Shadow M3100 9 Speed Rear Derailleur offers riders smooth and reliable shifting over varied terrain. With its unique 'Shadow' clutch derailleur system, you'll find that dropped and caught chains practically become a thing of the past. While its low profile design belies its rugged toughness. With the Shimano Alivio Shadow M3100 9 Speed Rear Derailleur you can ride on mixed terrain knowing you'll be able to get to your destination.