Shepherd's whistle
They are also produced commercially. Simple whistles may cost less than 1 USD in bulk; expensive ones may be quite ornate. They are commonly made of plastic, aluminum, stainless steel, silver, brass, titanium, Corian, jade, buffalo horn and other materials.
Shepherd's whistle
The size of the whistle can vary to fit the mouth of the whistler. The whistle's shape is best described as a flat circle of material, folded in half on a center line. This forms a very narrow U-shape in cross-section. The open space between the two sides is quite narrow - approximately 4–5 mm. A hole is drilled about 5 mm from the fold, through the center line of both faces.