Page "Binary prefix" Paragraph 37

Any block size could be specified up to the maximum track length.

Since the block headers occupied space, the usable capacity of the drive was dependent on the block size.

Blocks (" records " in IBM's terminology ) of 88, 96, 880 and 960 were often used because they related to the fixed block size of punch cards.

The drive capacity was usually stated under conditions of full track record blocking.

For example, the 100 megabyte 3336 disk pack only achieved that capacity with a full track block size of 13, 030 bytes.