What is the maximum length of a flat according to USPS regulations?

The maximum length of a flat according to USPS regulations is defined as 15 inches. Flats are considered a specific category of mail that includes large envelopes, magazines, and similar types of items. This specification helps ensure that these items fit properly within the sorting and delivery systems used by the USPS.

Understanding the size limitations is essential for compliance with mailing standards, as exceeding the maximum dimensions can result in increased postage rates or the item being classified differently, which could affect its delivery. The postal regulations aim to streamline processing and handling; hence, knowing the correct lengths helps maintain efficiency within the postal service's operations. This is why 15 inches is the established limit for flats under USPS guidelines.