Which of the following items would fit within the maximum size limit for letters but could be considered a non-machinable item?

A thick invitation card fits within the maximum size limit for letters but is considered non-machinable due to its thickness and rigidity. Non-machinable items do not conform to the standard characteristics required for automated processing by postal machines. This can include dimensions and weight, but thickness often plays a substantial role in determining machinability.

Thick invitation cards typically have embellishments, such as embossing or additional materials, which can prevent them from being processed on automated sorting systems, thus leading to manual handling.

In contrast, standard paychecks, flat flyers, and light brochures are typically designed to be lightweight and thin, allowing them to be processed using postal equipment without encountering issues, thus qualifying them as machinable.