To allow the use of UPC barcodes on smaller packages where a full 12-digit barcode may not fit, a 'zero-suppressed' version of UPC was developed called UPC-E, in which the number system digit and all trailing zeros in the manufacturer code and all leading zeros in the product code are suppressed (omitted).[12] This symbology differs from UPC-A in that it only uses a 6-digit code, does not use middle guard bars, and the end bit pattern (E) becomes 010101. The way in which a 6-digit UPC-E relates to a 12-digit UPC-A is determined by the last (right-hand most) digit. It can only be used with UPC-A number system 0 or 1, the value of which, along with the check digit, determines the parity pattern of the encoding. With the manufacturer code represented by X's, and product code by N's then