The older 10 speed series STI shifters work with any rear derailleur from the 8/9 speed era, the later 10 speed (5700/6700 series) derailleurs don't work so well(if at all) as the cable pull differs.
10 speed road flat bar shifters will also work with any 8/9 & the older 10 speed rears also.
The older 10 speed series STI shifters work with any rear derailleur from the 8/9 speed era, the later 10 speed (5700/6700 series) derailleurs don't work so well(if at all) as the cable pull differs.
10 speed road flat bar shifters will also work with any 8/9 & the older 10 speed rears also.