The Patton Model WET-18-A are made of PVC, are 18 inches (45.7 cm) long, and are internally threaded. They attach directly to Waveguide Filters without the need for a separate coupling nut.
The WET-18-A (which has an internal body thread size of 1-1/8 inch, 18 NEF) fits the WGF-6, WGF-461 and WGF-4.
The WET-18-B (which has an internal body thread size of 1-5/8 inch, 20 NEF) fits the WGF-12.
Note: If you are installing a WGF into a wall that is up to 2.51 inches (6.38 cm) thick, consider the Waveguide Extension Nut (WEN) which provides an extension solution that maintains the mathematically calculated dimensions of the waveguide while creating a flush-mounted solution. Or if you are installing a WGF into a wall that is up to 12 inches (30.5 cm) thick, consider the Brass Waveguide Extension Tube (WEB).
