The small indention is where you should align your lower lip when you blow.
Sizes are in US and diameters(mm). Pick your size and print. I've test printed in PLA, PETG and TPU.
Smaller sizes may require a brim to properly print.
Enjoy!
User Tip: If no noise is being made, try using a hair dryer or lighter to remove any stringing that is hidden within the whistle ring.
Fun Fact: You can see this model on the Netflix show Fubar(Season 2). Go watch and see if you can spot it!
The author marked this model as their own original creation.