Small Business Dictionary

First-Class Mail

First-Class Mail in America spans a variety of sizes, shapes and weights, and is delivered exclusively by the United States Postal Service (USPS). First-Class Mail includes rectangular postcards, letters no thicker than 0.25-inches and weighing 3.5 oz. or less, large flat envelopes no thicker than 0.75-inches, packages weighing up to 13 oz., presorted mail for high-volume business mail, and Priority Mail delivered in 2-3 days in most locations.