In marketing jargon, product lining is offering several related products for sale individually. Unlike product bundling, where several products are combined into one group, which is then offered for sale as a unit, 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 a category has. 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.