"Yun Bei" is what we call this tea serving jug in Taiwan. Yun means "matching" and "bei" means cup or bowl, so in English it could be called "tea matching vessel."
 
Its purpose is to ensure that all diners drink the same tea, since by serving from the teapot, the Yun Bei will balance the flavours and aromas of the top of the teapot with those of the bottom. You can try pouring directly from the teapot into two cups, one after the other, and you will notice differences in the tea in each one. Hence the reason for using this accessory when preparing Gongfu style tea.
 
This classical style porcelain Yun Bei has a comfortable handle that makes it easy to use. It is also adorned with the profile of Shennong, the patron saint of agriculture in Asian cultures. He is also credited with the discovery of tea. It is said that she discovered healing properties by testing more than 70 poisonous herbs on her body and was cured by drinking the infusion of tea leaves that fell into the container where she was boiling water.
 
It has a capacity of approximately 150 cc, occupying more or less half of it, so it is a good accessory to accompany our 100 to 150 cc teapots that you can find on this link.