But to qualify for mailing at the First-Class Mail postcard price, it must be: 1  Rectangular. 2  At least 3-1/2 inches high x 5 inches long x 0.007 inch thick. 3  No more than 4-1/4 inches high x 6 inches long x 0.016 inches thick.
eligible - qualified for or allowed or worthy of being chosen; eligible to run for office; eligible for retirement benefits; an eligible bachelor. qualified - meeting the proper standards and requirements and training for an office or position or task; many qualified applicants for the job.
fit or proper to be chosen; worthy of choice; desirable: to marry an eligible bachelor. Synonyms: suitable, fitting. Antonyms: ineligible, unsuitable, unacceptable. 2. meeting the stipulated requirements, as to participate, compete, or work; qualified. 3. legally qualified to be elected or appointed to office: