What is considered a standard letter size for mailing with USPS?

The standard letter size for mailing with USPS falls within the dimensions specified in the correct choice. Standard letters must adhere to specific size criteria to qualify for letter rates, which are typically designed to streamline processing and delivery.

The size range of 4.25 x 11 inches to 6.125 x 11.5 inches aligns with USPS regulations for standard letters, including both the minimum and maximum measurements. These dimensions allow for efficient handling and sorting in postal systems, making them the optimal choice for typical correspondence, such as bills, notices, or letters.

In contrast, the other choices do not meet the USPS guidelines for standard letter mail. Those options reference dimensions that exceed either the minimum or maximum limits set by the USPS, thereby categorizing them as different types of mail, such as flats or packages, rather than standard letters. Understanding these size regulations is crucial for ensuring proper postage and avoiding delays in mail delivery.