LC[x] and Classic both use the SuperDrive/3.5HD floppy mechanism, Lisa 3.5" uses the SSDD Apple 400k (hacked up from the standard 360k so Apple wouldn't have to redo the ROMs when they dropped Twiggy). a 800k external drive can be plugged into the classic, possibly (other compact Macs take it, as does the IIcx/ci), or a non-FDHD SE, original II, or <= Mac Plus machine come standard with 800k (or 400k) drives. Reminder for people who don't work with Macs much - stuff gets written to disk (When a System 6 disk is put in a System 7 Mac, the desktop file is immediately recreated) without the explicit intervention of the operator. If this is done on a SuperDrive Mac, and the disk is then put back in a 400/800k Mac, it won't be able to read/mount the disk. Write protect all 800k floppies if you use them in a 1.4 MB Mac.