In marketing jargon, product lining refers to the offering of several related products for individual sale. Unlike product bundling, where several products are combined into one group, which is then offered for sale as a units, product lining involves offering the products for sale separately. A line can comprise related products of various sizes, types, colors, qualities, or prices. Line depth refers to the number of subcategories under a category. Line consistency refers to how closely related the products that make up the line are. Line vulnerability refers to the percentage of sales or profits that are derived from only a few products in the line.