https://www.recordingthemasters.com/store/audio-cassettes/fox-c60-type-1/
Width: 3,81mm
Length: 86m
Recording time: 60min max
Clear 5-screws tabs-in cassette
Base film: Polyester
Base film thickness: 12 μm
Coating thickness: 4,7 μm
Total thickness: 16,7 μm
Coercivity: 370 Oe
Saturation retentivity: 1480 G
Oxide: Fe2O3

これだけ見るとSony AHFあたりのグレードとほぼ同等に見えるが？