Prime 9 Technology is a counter-intuitive philosophy based on the less is more theory - it embraces range without adding complexity Intended for use with Box Components` Prime 9 speed group, no compatible with other 11-50 cassettes Carbon fiber / nylon composite, steel, aluminum alloy construction Adjustable Tri-Pack limited slip clutch Forged inner and outer cage Pivot-Tech cable stay Precision sealed bushing pulleys 9sp 50 Long 2to1 BLK