Leaders of enduring firms know how to manage effectively their existing capabilities to achieve their strategic ambition and to serve their customers better than their competitors. Capabilities are made of resources and skills. Resources are what a company owns, while skills are what it can do. Identifying capabilities is a prerequisite to using them well. The inventory is based on an analysis of their contribution to creating solutions that are valued by customers and better than those of competitors. Resources and skills require different management but the key to sustainable success lies in combining them effectively. Resources serve to build a strong dominance over competitors. Durable firms manage them in following eight key principles: Threshold, Exclusivity, Critical Mass, Capabilities Rationing, Alignment, Valorization, Constant Flexibility, and Singularity. Enduring companies continually improve the quantity and quality of their capabilities.