Thermoset urea resin was used as the plastic material used in tape recorders when they were under development. It was also used widely from control knobs to handles with embedded metal and molded parts were also used in some surface panels. The coefficient of thermal expansion for urea resin is high and it is known to be a resin with large expansion and contraction. In winter, numerous cracks would start to appear at fixation points. Out of necessity, the hole sizes at the points of fixation were enlarged slightly and incorporating a certain amount of play for mounting, variations between summer and winter could be accommodated. However, polystyrene soon emerged and urea resin became something completely of the past.