Section 11(1) in The Indian Post Office Rules, 1933
(1)Single and reply cards of private manufacture may be transmitted by post as post cards:Provided that -(a)The postage shall be prepaid in full:(b)Their dimensions shall be 14cm * 9cm and they shall have the legend, "Post card" written in Hindi or English or printed on the address side.(c)As regards substance, they shall be neither thinner nor more flexible than the inland post cards issued by the post office.
