Deciding which products are core is the sticky point. Simply replacing established brands with new, improved formulas can be unnecessarily risky. New Coke (more recently known as Coke II) is a prime example of a “better” product that encountered unexpected resistance. On the other hand, Diet Coke was the most successful soft-drink introduction for decades. Contrary to the predictions of some positioning gurus, it beat Tab cold. Perhaps Coke II would have been more successful if the company had initially given consumers a choice between formulas. Product-line extensions can be effective ways to test-market product improvements and at the same time address emerging segments.