The SHIMANO ALTUS M310-Smart rear derailleur has a Wide Link design for increased rigidity and precise shifting. Key points Wide Link design for more rigidity and precise shifting Advanced light action 13/13T pulley (RD-M360) MegaPulley (RD-M310) Oversize 15-teeth tensioner and 13-teeth guide pulleys reduce noise and wear SMART CAGE pulley plate (RD-M310) Total capacity: 43T 8/7 speed