Yak is also called Tibet yak, horsetail cattle, which live in cold area with altitude above 2100 to 6000 meters mainly in Himalayas and Kunlun Mountains. Yak grows coarse hair in outer and fine thinner hair inner which is yak hair. Yak hair is black, dark brown or mix color of black and white, rarely pure white.

China is a country with large yak hair production. It is showed by statistics that China yak accounts for 92 percent of the world total amount and each adult yak can produce 0.75 to 1.5kg coarse hair and about 0.5kg fine hair.

Yak hair has similar structure with ship wool, with oval or round shape. The thickness and the length of yak hair is different if they are taken from different part of the yak body or yak is from different area. The finest hair can be 7.5 microns, mostly range from 30 to 35 microns. The average fineness is around 18 micron. The content of fibre with thickness around 30 to 35 micron is most and is hard to remove, therefore the coarse hair content is high. It is regulated that the fibre over 35 micron is yak wool and that below 35 micron is yak hair. The thickest yak fibre is over 100 micron.