What goes wrong

A reason was assumed rather than named

On this page11

The space was treated as self-evidently fine Settling was asserted without measurement Protection was claimed for a robust product A nice pail was called a reusable container Reason six was read as a preference And the machine reason was stretched The opening sentence was skipped A clear container was assumed to be exempt from everything And the state label rules were assumed to be federal Name the reason, and write it down References

For reasons other than the six. Which makes the list closed.

The space was treated as self-evidently fine

Nonfunctional slack-fill is the empty space filled to less than capacity for reasons other than the six listed. So the space needs a reason from the list.

Settling was asserted without measurement

Reason three covers unavoidable product settling during shipping and handling, and unavoidable is the limiting word. Settling you could design out is not obviously covered.

Protection was claimed for a robust product

Reason one is protection of the contents. A hard biscuit that does not break has less need of headspace than a freeze dried piece that does.

A nice pail was called a reusable container

Reason five requires the container to be part of the presentation of the food and to have value both significant in proportion to the value of the product and independent of its function to hold the food. That is a high bar.

Reason six was read as a preference

It is phrased as an inability to increase the fill or to further reduce the size of the package. Both limbs have to fail, not just the convenient one.

And the machine reason was stretched

Reason two covers the requirements of the machines used for enclosing the contents, which is clearance the filler actually needs rather than the clearance the line happens to leave.

The opening sentence was skipped

A container can be so made or so formed as to be misleading without any slack-fill question arising. Two of the three verbs are about the container.

A clear container was assumed to be exempt from everything

Paragraph (a) attaches its test to containers that cannot be fully viewed. The opening sentence has no such condition.

And the state label rules were assumed to be federal

The guaranteed analysis, nutritional adequacy statement and feeding directions come from state feed law. Only the container question is in the CFR section quoted here.

Name the reason, and write it down

Which is the practical discipline. A gap with a named, measured reason is a different thing from a gap.

References

21 CFR 100.100(a), the six functional reasons, verbatim: "(1) Protection of the contents of the package; (2) The requirements of the machines used for enclosing the contents in such package; (3) Unavoidable product settling during shipping and handling; (4) The need for the package to perform a specific function (e.g., where packaging plays a role in the preparation or consumption of a food); (5) The fact that the product consists of a food packaged in a reusable container where the container is part of the presentation of the food and has value which is both significant in proportion to the value of the product and independent of its function to hold the food; (6) Inability to increase level of fill or to further reduce the size of the package (e.g., where some minimum package size is necessary to accommodate required food labeling)". law.cornell.edu

21 CFR 100.100, "Misleading containers": "A food shall be deemed to be misbranded if its container is so made, formed, or filled as to be misleading." Paragraph (a) continues: "A container that does not allow the consumer to fully view its contents shall be considered to be filled as to be misleading if it contains nonfunctional slack-fill. Slack-fill is the difference between the actual capacity of a container and the volume of product contained therein. Nonfunctional slack-fill is the empty space in a package that is filled to less than its capacity for reasons other than:" law.cornell.edu

Written from 21 CFR 100.100 and from the catalog as it stood on 19 October 2026. That section concerns misleading containers and is not a pet food labeling guide: the guaranteed analysis, nutritional adequacy statement, feeding directions and ingredient definitions that govern a pet food label come from state feed laws and the AAFCO model regulations, which are not federal and are not described here. Our capacity field is the actual capacity of the container, which is one of the two terms in the regulation's own definition of slack-fill; the other is a property of your product.