Best printed using a resin printer, but I've had great success using a filament printer to make pens with, using PLA. I recommend using rainbow colours and printing in white filament/resin.
The half model is specifically sized for Slimline/Streamline pen kits, print two per pen. I remixed the larger model from the smaller for bespoke kits.
Models created in Sketchup by myself, use as you like.
The author hasn't provided the model origin yet.