facilitate transactions of tangible goods without maintaining real inventory. Some non-digital products have been more successful than others for online stores. Profitable items often have a high value-to-weight ratio, they may involve embarrassing purchases, they may typically go to people in remote locations, and they may have shut-ins as their typical purchasers. Items which can fit in a standard mailbox—such as music CDs, DVDs and books—are particularly suitable for a virtual marketer. Products such as spare parts, both for consumer items like washing machines and for industrial equipment like centrifugal pumps, also seem good candidates for selling online. Retailers often need to order spare parts specially, since they typically do not stock them at consumer outlets—in such cases, e-commerce solutions in spares do not compete with retail stores, only with other ordering systems. A factor for success in this niche can consist of providing customers with exact, reliable information about which part number their particular version of a product needs, for example by providing parts lists keyed by serial number. Products less suitable for e-commerce include products that have a low value-to-weight ratio, products that have a smell, taste, or touch component, products that need trial fittings—most notably clothing—and products where colour integrity appears important. Nonetheless, some web sites have had success delivering groceries and clothing sold through the internet is big business in the U.S. Aggregation High-volume websites, such as Yahoo!, Amazon.com and eBay offer hosting services for online stores to all size retailers. These stores are presented within an integrated navigation framework, sometimes known as virtual shopping malls or online marketplaces. See also Bricks and clicks business model Dark store Digital distribution Electronic business Online auction business model Online music store Online pharmacy Online shopping malls Online shopping rewards Package delivery Personal shopper Product tracing systems: allow to see source factory of a product Retail therapy Types of retail outlets References External links Consumer behaviour Merchandising