This is a perfect material for large patterns. Yak hair is very long and translucent like polar bear hair. Hair length is amazing 20-25 cm.
Yak hair is a good choice for big streamers and pike flies. It can be used also in tube flies and salmon flies. Yak hair won't absorb water, which makes it easier to cast.
Yak hair flies will not collapse in the water, so flies will have a big profile. Big profile is very visible in the water and fish will also "hear" the vibration from the fly.