This design I made is The Twitter King . It can tweed "Mimic"100'ts of bird calls just put some water in it . you must drill a 3 mm hole on the top of the head. for ABS use acetone to make it waterproof. important:  first fit the insert in the flute and test than acetone. fitting is done using a nail-file on the insert block I file the flat side a bit so the blow hole gets a bit bigger, adjust till it whistles!don't forget to close the back end of the tube with your finger while testing. I tested it for hours and its amazing that some birds come and look ! This is a nice present for young and old. and a really good deal for I designed and tested for 2 weeks