Metal Slide Whistle with Plastic Slide Whistle Bundle Metal Slide Whistle / Plastic Slide Whistle Metal Slide Whistle, as easy to play as it is to whistle or hum a tune. Play your favorite tunes or whistles for sound effects. Approximately 12.75" long when not extended. Plastic Slide Whistle, Unique instrument plays like a trombone. Play any song or use to create unusual sound effects. Great introductory instrument for preschool and elementary students. Perfect package for children ages 3 and up