Effective April 24, 2008, we are revising Mailing Standards of the United States Postal Service, International Mail Manual(IMM®) 260 to clarify the weight limit for single items placed in direct sacks of printed matter to one addressee (M-bags).
While the maximum weight for an M-bag is 66 pounds (including the tare weight of the sack), the maximum weight of individual items within a sack is implied by Universal Postal Union and Postal Service™ standards but is not clearly stated.