Origin NDC Sacks: Required, no minimum. Labels: Line 1, use L601, Column B. For Line 2, use “STD IRREG NDC.” Price: Irregular Mixed NDC | Mixed NDC Sacks: Required, no minimum for all remaining mail. Labels: For Line 1, “MXD” followed by L601, Column B information for the NDC serving the 3-digit ZIP Code prefix of the entry Post Office. For Line 2, use “STD IRREG WKG.” Price: Irregular Mixed NDC |