GUO in Chinese means both fruit and wrapping safeguard. GUO mask is designed for children. Kids can choose the different fruity flavors filter papers: peach, lemon, kiwi, and orange. The flavor is designed gentle and comfortable, which tends slight with the filter working out. When the flavor is totally gone, it is time to change the filter paper. Besides the filters, there are different colors of mask of GUO: orange, pink, lemon yellow and grass green.