Leister UNIDRIVE 500 120v Semi-automatic Roofing Heat Gun Welder 163.148 The new UNIDRIVE 500 is a semi-automatic advanced Leister heat gun roof welding machine for single ply (TPO, EPDM, PVC etc) roofing jobs. It has been designed in collaboration with industry practitioners and tradespeople like you to provide a solution for faster job completion but with better quality and more consistent results. The result was a single ply membrane roofing tool that bridges the gap between Leister heat guns like the TRIAC and fully automatic machines, designed for large scale commercial roofing jobs, such as the VARIMAT V2 and UNIROOF. The UNIDRIVE 500 provides a balanced application of pressure, through its dual hand/single hand grip design. This makes it very suitable for accurate seam welds around parapets, circle welding and close to the edge welding runs. In addition it has a reversible drive, with the nozzles able to weld in both directions, making this tool superb at detail welding, sky li