In addition to reducing the time which the customer spends at the checkout, computer linked scanners can instantly transfer the item sold from stock records to sales records. Not only does scanner technology add to customer convenience, it also provides the seller with a level of detail on inventories and sales which can significantly improve profitability. Scanners enable the distributor to not only record the product sold, or held in stock, but the pack size and the form of package. Thus, for example, a retailer using scanners will know that it is the 2 litre milk packs which are gaining in sales volumes whilst, perhaps, the 250 ml packs are increasingly slow to move off the shelves. This helps the retailer respond more quickly to changing consumer preferences and at the same time improves profitability through reducing wastage rates.