Flextone Bone Collector Bull Collector Elk Call Designed to make all elk sounds. It's Mylar reed system allows you to bugle like a big bad herd bull. By simply adding or decreasing airflow and pressure you can sound like a smaller satellite bull. Simply pop off the mouthpiece and you are ready to mew like a cow or chirp like a calf. Do aggressive estrus cries of a hot cow in heat begging for company from the herdbull.