I’m always looking for the smallest linewidth and the hit-tec-c .25 has been my favourite so far. The Jetstream is new to me as is the Kleid notebook - looking foward to trying them out!
How about you? Any favourite super fine lined writing instruments you like to use?

Love my G-Tec-C4 0.4. My local store doesn’t sell the Hi-Tech-C, so my 0.4 is as thin as it gets for me. Of course, I could order some but I had a bad experience with that so not doing it again soon.
Do you write on lined paper? If so, do you use lines with less space between them?