Wil-Key Extrusion Welder Model WK-EX850 is a portable and lightweight extrusion welder commonly used for geomembrane lining repair work, old corner welding and detailing works. WK-EX850 extrusion welder rod feeder is built to suit 3mm to 5mm diameter welding rods. The welder comes with optional hot air blower attached to it. Other optional items include different shape Teflon nozzles for welding on flat area, corners, angles etc.