First Class Package Service is a fast, affordable delivery service for packages weighing up to 15.99 ounces. This mail class offers 1 to 3 day delivery within the U.S. and includes free USPS Tracking. Changes to First Class Package Service in 2016 Maximum Package Weight Increased to 15.99 Ounces USPS has introduced a new maximum weight … Continue reading First Class Package Service: Summary of 2016 USPS Rate Increase