Acera mountain bike rear derailleur with light action operation and over-size pulleys for a wide gear choice. The world's best known manufacturer of bicycle components, Shimano remain at the forefront of component development and production. Synonymous with smooth shifting and high quality, Shimano is a brand without compare. Features: Oversize 13-tooth tension and guide pulleys to reduce noise and wear. Extension spring and low-friction fluorine-coated link pivot bushing result in a light shifting action. Top normal spring for use with Rapidfire shifters. IG and HG chain, 7- and 8-speed compatible. For use with 28 to 34 tooth low rear sprockets, total capacity 43 teeth.