Page "Compact Cassette" Paragraph 21

Other lengths are ( or were ) also available from some vendors, including C10 and C15 ( useful for saving data from early home computers and in telephone answering machines ), C30, C40, C50, C54, C64, C70, C74, C80, C84, C100, C105, and C110.

As late as 2010, Thomann still offered C10, C20, C30 and C40 IEC Type II tape cassettes for use with 4-and 8-track portastudios.