There *is* only one model of 9-speed bar-end: Dura-ace (SL-BS77). They work in all Shimano 9-speed setups with all Shimano indexed rear derailers *except* pre-9-speed Dura-ace. For the pre-9-speed Dura-ace (RD-7400), they actually shift 8-speed spacing. Before 9-speed, Dura-ace shifters only worked with Dura-ace rear derailers and that is probably the origin of the statement.