Shimano FD-6503 is a front derailleur designed for triple front chainwheel use, providing smooth and precise shifting between chainrings. It's compatible with Shimano's ULTEGRA series components, including ST-6500 shifters, SP40 outer casings, and CN-HG92 or CN-7700 chains. The derailleur features a band-type or brazed-on type mounting system, suitable for a front chainwheel tooth difference of up to 22 teeth. It ensures optimal performance when paired with a 45mm chain line and a chainstay angle between 53 and 56 degrees.