Microdrive, IBM DSCM-11000, with 1GB capacity. From year 2000. Connector type is “CF+ Type II”. Formfactor 1.8’’. Weight 16 gramms.
These are real harddiscs, with super-small rotating discs inside, moving heads and all that fancy stuff.
This was designed at a time, where it was not possible to create large semiconductor based non-volatile memory.
At that time, it was easier to scale down the physics of a real harddrive and to create a tiny version of that.
The selling price for this disk in 2001 was about 1000 Deutsche Mark, so roughly 500 Euros.
To use the microdrive in a PC, you need an adapter between the CF connector of the drive and e.g. an PC Vard connector located in older notebooks.
Protecting cases for both drive and adapter: