Follow the link for the information. It is worth the $20.
http://skoalongcut.blogspot.com/2015/04/hands-free-easy-to-use-grunt-call.html
http://skoalongcut.blogspot.com/2015/04/hands-free-easy-to-use-grunt-call.html
Any issues with the tube cracking or degrading?
Is the tube replaceable? It looks like it might be in the pic.