second line. The price of the royal gold medal doors and windows is 8-2 yuan, so it does not belong to the first line. Moreover, the popularity of Royal Gold Doors and Windows is not high, so it is not a first-line brand, but a second-line brand. Doors and windows are divided into enclosure components or partition components according to their different positions, and have different design requirements to have the functions of heat preservation, heat insulation, sound insulation, waterproof and fire prevention respectively.