Colin Ultra pac has been by far the best product for poly prop for years now.New Look, Nearly all cheap poly rugs are power loomed these days and the warp and weft are cotton or nylon, hessian/jute is not used that much now. Therefore you will not shrink one. They usually buckle abit on cleaning especially if the truckmount is throwing alot of heat out but they go back on drying.Oh on cleaning a few hundred B/W carpets ,ive never shrunk one yet