柚子 (pomelo) is associated with the Mid-Autumn Festival in China, where it is a traditional offering and gift. Its round shape symbolizes family reunion. Note: in Japan, 柚子 (yuzu) refers to a different citrus fruit entirely.
usage
In mainland China, 柚子 almost always refers to pomelo (Citrus maxima). Do not confuse with 日本柚子 (yuzu), which is a smaller, aromatic Japanese citrus.