Applicability of the New Rules. The new cargo securement rules apply to the same types of vehicles and cargo as the old rules, covering all cargo-carrying commercial motor vehicles (as defined in 49 CFR 390.5) operated in interstate commerce.
Most commercially-produced postcards measure approximately 4.21 inches by 5.47 inches. Less commonly, smaller postcards are typically 3.5 inches by 5.5 inches, close to the minimum size the USPS allows.
The U.S. Postal Service allows customers to use the postcard rate for First-Class Mail for postcards that are at least 3.5 inches high by 5 inches wide but no more than 4.25 inches wide by 6 inches wide. As of April 2014, the postage rate for a postcard of this size is 34 cents. USPS also has a First-Class rate for large postcards that are no more than 6.125 inches high by 11.5 inches wide by 0.25 inches thick. These postcards cost 49 cents to mail as of April 2014. Learn more about Postal Services