Yeah the key differentiator was that the other hard disk MP3 players up to that point used 2.5" laptop harddrives and removable AA batteries and fit in a cargo

Yeah the key differentiator was that the other hard disk MP3 players up to that point used 2.5" laptop harddrives and removable AA batteries and fit in a cargo pocket. The iPod used a 1.8" harddrive and a slim built-in rechargeable battery and fit in a jeans pocket (it was pretty huge for a shirt pocket but could fit in there if you didn't care about it ruining your lines). The term "laptop harddrives" of course confuses the issue: the Macbook Air first shipped with a 1.8" harddrive before it changed to flash storage.