Record the extent of the resource by giving the number of units and an appropriate term for the type of carrier as listed under 3.3.1.3. Record the term in the singular or plural, as applicable.
⮚Current serials.
For current serials, the extent (subfield $a) is required only for tangible non-print serials. If supplied, it contains only the designation for the type of resource.
...
300 ## $a CD-ROMs [use of the term in common usage]
⮚Ceased Serials.
If a serial has ceased publication or the record is continued by another due to a major change, record the number of (bibliographic) units published, when this information is available.
...
When the total number of units is uncertain or unknown, omit this information. This area does not have to be completed when closing off a record if the information is unavailable or difficult to determine.
300 ## $a volumes
⮚Illustrations and other Content (300$b)
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300 ## $a volumes : $b illustrations
300 336 ## $a text $b txt $2 rdacontent
300 336 ## $a still images $b sti $2 rdacontent
⮚Dimensions (300, subfield $c)
Height. The height, given in centimeters, is given for purposes of shelving, since publications that are very large or very small may require special shelving, and for purposes of identification. If the height includes a fraction, round off to the next whole centimeter (RDA 3.5.1.3). If a serial is bound by a publisher, measure the bound volume, but do not measure in-house binding.
Height and Width. Following RDA 3.5.1.4.14, record both the height and width when the width is less than half the height or greater than the height; record as height x width. Record the height and width also when the serial consists of a single sheet (RDA 3.5.1.4.11). If intended to be folded, give the height when folded.
300 ## $a volumes ; $c 20 x 32 cm
300 ## $a volumes ; $c 21 x 34 cm folded to 8 cm
⮚Changes in the Dimensions
If the height changes, record the lesser height followed by the greater, regardless of the chronological sequence.
Earlier dimension: 29 cm; Later dimension: 26 cm
Record: 300 ## $a volumes ; $c 26-29 cm