The TF85/TZ85/TK85 are all the same basic drive, with DSSI/SCSI/STI interfaces respectively. Everything up to the TZ87 can read TK50 (CompacTape) and TK70 (CompacTape II) carts. The TZ87N was a cost-reduced TZ87, some of the cost saving coming from dropping the backwards compatibility. Beyond the TZ87N, nothing (AFAIK) can read TK50 or TK70 carts. Antonio