Volatile markets and the integration of products into cyber physical systems state new challenges for companies. Especially products with long development times are more difficult to design since the quality of market forecasts decreases and the rate of change increases. It becomes necessary to continuously develop products and implement smaller changes according to current market trends to keep them attractive and remain able to offer them at a competitive price. To manage the challenging market development, companies need to increase their flexibility. Therefore, the product family and the production system must be redesigned together to facilitate the implementation of unpredictable product changes in the product family and the corresponding production system. This paper presents a case study conducted at a German car manufacturer, which is used to derive criteria for the comparison of modular product concepts in terms of flexibility from a product development and production perspective.