Saw a crew of electricians use one of those to pull some big service cable into a long run of PVC conduit once. The pull failed about 3/4 of the way through with a big bang and the machine stalled. When they went to investigate, the cable had "sawed" through the conduit at bends and was sawing into the straight sections. When the cable got to that point is was actually pulled out through the side of the conduit. Not sure why they had used PVC for that??