Unsealed letters sent by a blind person or a person having a physical impairment, as described in section 3403(a)(1) of this title , in raised characters or sightsaving type, or in the form of sound recordings, may be mailed free of postage. ( Pub. L. 91–375 , Aug. 12, 1970 , 84 Stat. 758 .) Statutory Notes and Related Subsidiaries Effective Date Section effective July 1, 1971 , pursuant to Resolution No. 71–9 of the Board of Governors. See section 15(a) of Pub. L. 91–375 , set out as a note preceding section 101 of this title . CFR Title Parts 39 20 , 111 , 113 , 255