For many companies, it is a challenge to balance product variety and cost, i.e. external and internal efficiency. Product platforms has been the dominant solution for a business targeting mass-customization. The main idea is to dived the product into modules that can be shared among different product variants. This has been a success on the consumer market, however, many manufacturing companies are engineer-to-order (ETO) oriented, such as original equipment suppliers (OES). They design a unique solution, often in close collaboration with other companies, based on different product concepts and/or core technologies. For these companies, there is a strategic need for a platform model influenced by the principles of masscustomization, although, not limited to only include modules. In this work, a novel platform model, called Design Platform is described. The model has been developed and applied in cooperation with four companies. The Design Platform provides a coherent environment for management of heterogeneous design assets to be used in product development and supports an improved ability to master fluctuating requirements and systematic introduction of new technologies.