Thankyou so much for this! I have type 1 and use Fiasp and also Optisulin in Novo pens. I use a half unit pen for Fiasp so I have to use a permanent pen with penfills rather than the disposable pens, and I'd struggled when I first got diagnosed to not hurt myself since the Novo permanent pen is so much heavier than an Optisulin disposable pen, so to make them the same weight my husband had jerry-rigged a second Novo pen to work with an Optisulin cartridge, and I've just been keeping that going for years. Unfortunately the little bits we'd added recently broke and I couldn't put it back together so this came in super handy! Pic shows the difference between the Novo cap (the red) and this cap (the black). I printed in PETG because I was too lazy to change my filament, it worked a treat, I had a couple of globs but they filed off really easily (I'm still playing with my PETG settings so there's no doubt a me thing). I added the spacer as well since I'd printed it, but it works with or without. You've really gotten me out of a jam, thankyou so much for sharing this print, I really, really appreciate it <3