N20 cartridge pen
thingiverse
How to make the pen: http://www.hassanportal.tech/2021/06/14/how-to-make-a-pen-from-a-whippet-n20-cartridge/ This is a pen which can be made from a used N20 cartridge. It allows the ink cartridge from standard BIC pen to fit snugly inside the cartridge. Just drill out the centre hole of the canister with an M5 drill bit or bore it open with a Victorinox tool then just print the adapter at the given resolution and fit them in.
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