Nonmachinable surcharges are applied to First-Class letters when the item is?

Nonmachinable surcharges are applied to First-Class letters based on specific characteristics that prevent them from being processed by automated systems. When an item is polybagged or poly wrapped, it often does not meet the requirements necessary for machines to handle it effectively. This can include issues such as the item being too flexible or having an irregular shape that can get caught in sorting machines.

Polybags or poly wraps can create problems during automated sorting processes because their materials and shapes can be inconsistent, causing them to jam machines or be misrouted. Therefore, items that are packaged in such a way typically incur a nonmachinable surcharge to account for the additional handling and processing required to manually sort them.

In contrast, the other choices pertain to types of packaging or formats that are generally not classified as causing such issues, which is why they do not lead to the imposition of nonmachinable surcharges under standard postal regulations.