The whistles are hand produced out of a clinical mineralized polymer sheet. The material is commonly seen in the household and medical environment. A tasteless product in an array of one of colors. The BREFI whistle has been designed to have an excellent pitch and sound. They are equal to the horn whistle and better than most on the market. A good whistle for all weather, keeping a standard even temperature in the coldest and warmest environments. All whistles have been hand crafted by master crook and whistle maker Dafydd Davies from Wales.