Final answer:
First class mail has a weight limit of 13 ounces.
Step-by-step explanation:
The requirement that first class mail has is that it must weigh 13 ounces or less. For example, if you want to send a letter or a small package using first class mail, it should not weigh more than 13 ounces. If the item you are sending weighs more than 13 ounces, you may need to use a different mail class, such as Priority Mail or Priority Mail Express.