Provided is an apparatus and method of transmitting a packet of a node in a wireless sensor network. The core includes a center having a center hardness of 50 Shore C or greater and formed from a first HNP composition, and an outer core layer having a surface hardness of 75 Shore C or greater and formed from a second HNP composition. The selective filtering apparatus comprises an input interface connectable to a source of a composite signal within a first frequency range and a filtering device, coupled to the input interface. The coextrusion structure may also include one or more removably disposed, flow-shaping inserts, and the partition member may be a removably disposed partition plate.