BarCode POSTNET (US Post)
POSTNET is the Postal Numeric Encoding Technique used by the United States Postal Service (see also USPS Intelligent Mail). Each of the 11 digits is encoded in five bars, two of which are always full-height bars. (It sometimes referred to as "2 out of 5" code, not to be confused with '2 of 5' codes!) The barcode consists of ZIP code/delivery point data followed by a check digit, topped and tailed by guard-bars (62 bars in all).
BarCode plugin can generate a barcode from ZIP code data and compute the check digit itself, if required.
The size of the bars/barcode is rigorously defined: there are no options for modifying it.