The integration of CAD and CAPP is difficult because semantic information is usually lost after the data is transferred from CAD to CAPP. The application of features has been proven in avoiding this obstacle. However, due to the great variety of products, it is necessary that the user is able to generate new features and modify existing ones easily. Therefore, this paper introduces a concept for the employment of user defined features in the CAD-CAPP chain. To enable the user to define new features, a feature editor is provided. In order to have a system neutral representation, an EXPRESS based formal description language has been developed. Current emphasis is put on the direct connection of features with the feature related manufacturing knowledge, hence the greater part of the CAPP knowledge is configurable via the exchange of the feature library. The CAD system can evaluate the knowledge to support the user in better design for manufacture.