The concept of barriers to entry is, perhaps, the most daunting proposition an innovator must face. Incumbent companies run by deep, experienced management teams dominate almost every industry. Yet, time and again, upstarts find a way to prevail. How do they create disruption? Bain's experience and analysis suggest that customer focus holds the key. Successful challengers target specific segments and design propositions that address customers' unique concerns in ways incumbents don't—and very often can't.