I printed in PETG and it seems to withstand the heat well.
The ID is 6mm. The OD of the tip is 5.5mm. It can be a loose fit depending on your printer tolerance. The tip don't move much once I tightened the tip screw on my Pinecil.
Not very ergonomic. The whole thing is long and tail-heavy.
The author hasn't provided the model origin yet.