This paper uses a large, representative sample dataset to investigate the relationship between product innovation, and three constructs developed to describe the openness of firm boundaries towards external knowledge and technology. Emphasis is put on identifying mplementarities; thus avoiding the limitations inherent when examining different dimensions in isolation. External search (1) and collaboration (2) diversity measure the extent to which different types of information sources and collaboration partners are used. Both impact the likelihood of new product introduction positively, and are complementary to each other. External R&D (3) measures the relative importance of contract R&D, and is found to have a zero impact which turns positive and significant in interaction with search, but negative in interaction with collaboration. The methodology, findings and theoretical implications contribute to improving the understanding of how and why external interfacing impact innovativeness; and consequently how boundaries should be managed at the level of the organization.