Cannondale mountain frames 1991 2004upgrade or replacement rear derailleur dropouts stiffer and more rigid to improve shifting performance cnc machined from solid 6061 aluminium to exact tolerancesstiffer than any original equipment hanger which improves shifting performancestill breaks before your frame does to perform its main functionall hangers come with instuctions and hardwaredirect replacement for original equipment with guaranteed fitblack anodised for extra scratch and damage resista