I don't think this fountain pen is suitable for carrying around. I think it's a fountain pen that is best used on a desk. As for the nib, it has an old Montblanc 22 nib attached.
I think it's about M in thickness. Recommended for those who have knowledge of ink-stop systems. An eyedropper or syringe is used to inject the ink.
We also sell this product on a Japanese e-commerce site, so there is a possibility that it may be out of stock depending on the timing. Also, please understand the product details carefully before purchasing.