Nursery teacher's and instructor's to recommend whistle. Keep the holes with fingers like Samba whistle thing, 3 Pitch （ de, Les, MI ） of 吹き分け possible. In the friendly in the indoor sound and outdoor sound 吹き分け. New system instead of the traditional Cork in rotating pipe. Too wet in the pool I know wash OK so sanitary. Length 6 cm, width 4 cm, resistant to wet salt is a vinyl strap attached.