Customer Rating: 
Summary: These whistles have "balls"
Comment: Acme Thunderer whistles set the standard by which all other whistles are compared. They are quality made in Birmingham, England. Police, coaches and referees use these famous whistles all over the world.
The plastic model #660 is small, portable, easy to blow and inexpensive. It is tested and guaranteed to reliably produce a loud high pitch shrill. The internal ball is actually call a "pea". It is made from cork so that it is waterproof.
The Acme Thunderer Whistle is also made in Nickel plated brass called the model 60.5. It is sturdier due to its all metal construction but a little more expensive. Thunderer Whistle Chrome Nickel Plated
Acme also makes other larger lower pitch models.
Acme supplied the mates whistles in 1912 for the legendary ship Titanic used during its distress calls.
So get the best. Get a genuine Acme Whistle.
