DECtape
A reel of magnetic tape about 4 inches in diameter and one inch wide. Unlike today's macrotapes, microtape drivers allowed random access to the data, and therefore could be used to support file systems and even for swapping (this was generally done purely for hack value, as they were far too slow for practical use). DECtape was a variant on LINCtape.
In their heyday DECtapes were used in pretty much the same ways one would now use a floppy disk: as a small, portable way to save and transport files and programs.