Mini-cassettes? As in the mini version of regular cassettes, which

FastCap Mini Tape Measure ~ 6' - Standard Reverse

A Clockwork Orange — Beethoven Mini-Cassette

Transfer MiniDV and HDV digital video tape to .DV .MOV & MP4

Mini-Cassette - Wikipedia

Mini-Cassettes Buzzsaw (Transformers, G1, Decepticon

Micro and Mini Cassettes Transfer to CD

Microcassette size incompatable. - VideoHelp Forum

Incoming】Dr.Wu DW-P51M Chatter Shattered Glass Limited Version

Mini-Cassette - Transformers Wiki