EDDM must fit with a preexisting range of dimensions to be shipped. Mail must be rectangular, and a minimum of 11.5" long OR 6.5" wide OR .25" thick, and a maximum of 15" long OR 12" wide OR .75" thick. Additionally, each mailpiece must be at least 0.007” thick (approx. 3 sheets of copy paper) and cannot exceed 3.3 ounces.