by polymaker, published
This is a tool for the coolest instrument ever! ;) I measured everything to be the same size as my mouthpiece so I hope it works, though it may not sound as good as a metal one.
This is based off of an image(1) on Wikimedia by (2). Since the image has a creative commons share alike with attribution license I am obliged to use the same here.
Print it out and play away!