It is one of my favorite dry fly for grayling fishing. It works great for trout to, there is no doubt about that but is tied especially for grayling. What is the difference? Here it is: sparse hackle, delicate silhouette, delicate materials. Trout will brake this fly in parts because is not tied for him.
The secret in tying grayling flies is in making flies more close to the real ones. The body should be thin, very thin and delicate, very well balanced and just a turn of hackle. Anything too bulky or too overdressed will not work for grayling