Sheet is cut 12" x 15" Our most popular heat transfer film. Compare the ease of weeding and applying ThermoFlex® Plus with competitive products and discover why so many professionals ask for it by name. ThermoFlex® Plus is a durable polyurethane based material that is highly flexible. It has a soft hand and strong grip and if applied properly will outlast the life of the garment. ThermoFlex® PLUS will NOT adhere to nylon.