What manual should be used to look up postage prices and classes of mail transmitted within the US?

The correct choice for looking up postage prices and classes of mail transmitted within the US is the DMM, which stands for the Domestic Mail Manual. The DMM is the official guide that contains comprehensive details on postage rates, mailing standards, and classes of mail. It serves as a critical resource for postal employees and customers who need to understand how different types of mail are categorized and what the corresponding prices are based on factors like size, weight, and destination.

Using the DMM ensures that users have the most current and accurate information, as it is regularly updated to reflect changes in pricing and policies. This is essential for ensuring that customers receive the right services and pay the correct postage. As a foundational document for USPS operations, the DMM is also a useful tool for training and quick reference for window clerks assisting customers in mailing their items correctly.