The 1581 was the 3.5" floppy drive
for the C64 computer
Using 80 tracks with 10 sectors each, on 2 sides, it featured an astounding storage capacity of 800K, on a single floppy disk.
The 1581 is a wonderful item when you want to use all the nostalgia found in the games of the 80's, but can't manage to get those old tapes working. It's all on the Internet, ready for download.