Typical suitable polymeric materials out of which rigid intermediate sheath 32 can be extruded include polycarbonates, polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polyamides such as Nylon, which is a trademark of duPont, polyacetal copolymers, such as Celcon (trademark) copolymers of Celanese Corp., acetal homopolymers such as Delrin (trademark) polymers of duPont,