Compositional plug-and-play-like reuse of black box components requires sophisticated techniques to specify components. How to specify business components formally is proposed in a memorandum presented by the business components working group of the German Informatics Society (GI). Its main concept are introduced in the first part of this paper. So far not considered was the situation when a component allows adaptation by customizing (setting paramters). In the second part we discuss how the memorandum can be extended to specify customizing data of business components.