A postcar or post card is a rectangular piece of thick paper or thin cardboard intended for writing and mailing without an envelope and at a lower rate than a letter. Stamp collectors distinguish between postcards (which require a stamp) and postal cards (which have the postage pre-printed on them). While a postcard is usually printed by a private company, individual or organization, a postal card is issued by the relevant postal authority. The United States Postal Service defines a postcard as: rectangular, at least 3-½ inches high x 5 inches long x .007 inch thick and no more than 4-¼ inches high x 6 inches long x .016 inches thick; (in metric; 12.7 cm x 8.9 cm) however, some postcards have deviated from this (for example, shaped postcards).