Yak is a luxury fibre and is naturally brown to fawn in colour. The soft fine under hair is the desirable element of this animal's coat and is removed commercially by dehairing, which separates the soft under hair from the coarse outer hair, known as guard-hair.
Yak fibre sits in between camel and cashmere for quality at 17-19 microns and is used as a cashmere substitute, largely as a consequence of price.
These yak tops have been de-haired and bleached to acheive a white colour.