PLU codes are used primarily in retail grocery stores or supermarkets, where they are keyed into point of sale systems by cashiers or by customers at self checkout machines when the produce is being weighed or counted. The codes may be printed on small stickers, tags, or bands that are affixed to produce, or may be printed on signs. Since 2006, stickers with PLU codes may also have a GS1 DataBar Stacked Omnidirectional barcode