Story

One single continuous piece of tape, no spool, all zig-zaggy inside the case, that was quite literally shoved back into the cartridge as fast as it was being tugged out. 85KB capacity, IIRC. Innards of the drives visible here: http://www.binarydinosaurs.co.uk/scripts/picshow.php?image=qlmicrodrives.jpg&folder=/Museum/Sinclair/ql&back=/Museum/Sinclair/ql/index.php . Although initially developed for the BT Merlin and the Sinclail QL, I had one on my ZX Spectrum as I splashed out on Interface 1.

Dire is the only word for them.

However, the drives were significantly lighter than the 40kg unit which I used to read these: http://fatphil.org/images/im_floppier.jpg