The FiberPlex Technologies <strong>WEB-6</strong> extension tubes allow for easier pass through of fiber through thicker walls and penetrations. WEB tubes are made of brass and have external threads which match the WGF-6, WGF-461 and WGF-4. They require a WCN-6 Waveguide Coupling Nut to attatch them to the Waveguide Filter. The WET tubes are made of PVC and are internally threaded. These attach directly to a the Waveguide Filters without the need for a separate coupling nut.</p>