"What Our Gearhead® 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."