Shimano Cassette Sprocket CS-HG41 7-SPEED, 11-13-15-18-21-24-28T, 10 Piece Semi Bulk PackLighter weight (compared to CS-HG51-8I / HG40-8I / HG30-8I / HG30-7I)Long leg spacer for further weight reduction (CS-HG51-8)Enlarged sprocket window design for lighter weightVariety of gear combinationsHYPERGLIDEQuick assemble13T flat sprocket fixed with lower gears