In the field of inventory management, a stock-keeping unit or SKU is a distinct item for sale, such as a product or service, and all attributes associated with the item that distinguish it from other items. For a product, these attributes include, but are not limited to, manufacturer, product description, material, size, color, packaging, and warranty terms. When a business takes an inventory, it counts the quantity of each SKU. SKU can also refer to a unique identifier or code that refers to the particular stock-keeping unit. These codes are not regulated or standardized. When one company receives items from another vendor, it has a choice of maintaining the vendor’s SKU or creating its own. Other entity tracking methods, with varying regulations, are Universal Product Code (UPC), International Article Number (EAN), Global Trade Item Number (GTIN), and Australian Product Number (APN).