An IMb consists of a 20-digit tracking code field [Barcode Identifier, Service Type IDentifier (STID), Mailer ID (MID), and Serial Number] and a Routing Code (ZIP Code™) field of up to 11 digits. An encoder is required to convert the numeric digits into a 65-character string representing the bars of the IMb and a special font is required to convert the 65 alpha-character string into the IMb bars. Users can download the fonts and computer source code at https://postalpro.usps.com/mailing/encoder-software-and-fonts.
