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.