What is the maximum weight for first-class mail?

The maximum weight limit for first-class mail, specifically for letters, is indeed 13 ounces. This weight limit allows for a variety of items to be mailed, including standard letters, postcards, and small parcels. The 13-ounce limit is significant as it enables senders to use first-class service for lightweight packages that may contain important documents or items, ensuring they can be delivered in a timely manner. First-class mail is often favored for its relatively fast delivery and the reliability associated with it, making the 13-ounce weight threshold crucial for maintaining efficient mail operations.