usps first-class package service USPS First-Class Package Service is an affordable and reliable shipping option provided by the U.S. Postal Service. It is commonly used for sending lightweight packages, weighing up to 15.99 ounces. This service offers fast delivery, with packages typically arriving in 1 to 3 business days, depending on the destination. First-Class Package Service includes tracking, which allows both the sender and recipient to monitor the status of the shipment. It is often a cost-effective choice for small businesses and e-commerce sellers who need to ship products quickly and affordably. This service does not include insurance but offers a high level of reliability for everyday shipments.