These are large roll price labels used in Costco bakery departments for labeling baked goods and packaged items. Each roll contains 1,800 labels, and each case includes 5 rolls for a total of 9,000 labels per case. The "5.1" designation refers to the label size or format specification used in Costco's internal bakery labeling system. These labels are designed for use with Costco's standard bakery label printers to display pricing, product names, weight, and other required product information on bakery items.