There are two classes of barcode labels:
Photocomposed labels are made using a photographic process to create high-quality, long-lasting labels. Rather than printing ink on paper, the photocomposed process makes the barcode image an integral part of the label. These labels usually come with high-quality lamination and adhesives that make them durable and easy to attach. You should use photocomposed labels on all permanent items.
One-part labels include the library name, barcode, and written number. If you want to place a barcode label in two different locations on an item, you can order two copies of these one-part labels.
Two-part labels include the same information as the one-part label. But these have an additional part that displays the written barcode number again. The second part can be attached to a shelf list card or placed on the book in a different location than the upper portion. With two-part labels, you can have two labels for each item at a lower overall cost.