What Our Gearhead(R) Experts Are Saying: "I've put the Alivio RD-M3100 through some real trail abuse, and it's held up better than expected for a mid-tier derailleur. The Shadow design keeps it tucked away, shifts are clean, and it's easy to adjust mid-ride." When the trail turns unpredictable, we count on components that perform without distraction. The Alivio RD-M3100 9 spd Long Cage Rear Derailleur brings confident, reliable shifting with a low-profile design that holds up to aggressive riding and everyday miles alike. Engineered with Shimano's SHADOW RD tech, this derailleur hugs the frame to avoid rock strikes and chainstay contact-keeping the ride quieter and the drivetrain running smooth. Its long cage design accommodates wide-range cassettes up to 36T and offers a 45T total capacity, making it ideal for loaded touring bikes, mountain rides, and everything in between.