Here's a chart listing specs for most derailleurs. Find your current one on the left column yours is probably row 289 or 290, the very top line lists columns of single, doulble and triple chainring limits and the line below that lists various data to show what the specs of every derailleur listed. Anything that doesn't have a "pull ratio" of 1.7 is a no-go. Check the 'min and max low' for cog size limits. Microshift are good quality for what you need only because the 6500 Ultegra groupset has been out of production for over 20 years and Shimano changed the pull ratio for almost all their road groups after going to 11 speed in around 2013 so buying used can be risky. Doesn't matter if the derailleur came with a different speed groupset as long as the pull ratio is 1.7. https://docs.google.com/spreadsheets...#gid=847158527