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.
Whistle (company)
In April 2016, Whistle was acquired by Mars Petcare, the pet product subsidiary of the food and candybar maker Mars, for $117 million.