Shimano Acera RD-M3020-SGS Rear Derailleur - 7/8 Speed, Long Cage, BlackThe Shimano Acera RD M3020 rear derailleur features Double Servo technology to provide smooth, precise shifting and helps you ride challenging terrain with fewer interruptions. Double Servo mechanism enables the rear derailleur to move in an optimum path Versatile performance and wide compatibility SGS Long cage Product Specifics Rear Der Shifter Compatibility: Shimano Mountain Rear Derailleur Mount Type: 10x1 Standard Drivetrain Speeds: 8 Drivetrain