== S- and D-Drives (720K) ==
These are the first generation of 720K floppy disc drives from Vortex. They came in variants having either a single drive ("S" variant) or two drives ("D" variant). The "S" variant (as well as the less expensive "Z" variant) was delivered with the same double-height casing as the "D" variant, so that a second drive could be retrofitted. The 5,25" drives used were F1-S and -D variants are based on BASF 6138 (81690-001) type drives (, e.g. double-sided, double density, 80 tracks per side, 96 tpi).
=== Variants ===