Frame structures, assemblies and methods for use in implantable medical devices. The frames may include one or more first polymeric portions and one or more second polymeric portions coupled to the one or more first polymeric portions. The one or more first polymeric portions may have a higher durometer than the one or more second polymeric portions. The one or more second polymeric portions may provide an interference fit between the one or more second polymeric portions and the housing and/or between the one or more second polymeric portions and one or more components disposed in the housing.