What mail processing category would include letters and flats?

The mail processing category that includes letters and flats is specifically designated as "Letters/Flats." This category encompasses standard-sized letters and larger, flat-shaped mail pieces that require specific handling and processing techniques due to their size and shape.

Letters typically refer to standard mail items that meet size and weight guidelines, allowing them to be processed efficiently using automated systems. Flats are larger than letters but still fit within specific dimensions that permit them to be treated distinctly from parcels. This classification allows for effective sorting and delivery, as both letters and flats share similar processing requirements.

The designation of "Letters/Flats" signifies a streamlined approach to handling these types of mail, ensuring that they receive the appropriate treatment during the processing stages. This categorization is essential for efficient postal operations, as it helps postal services to implement the necessary logistics and technology for managing different types of mail efficiently.