I'm selling these because I rarely use them anymore. These are replacement nibs for Souverän M405 and M205 pens. They can also be used on the M400, but the color won't quite match. I used them by swapping them onto an M205, but I haven't used them much lately, so I switched back to the steel nib. I didn't use them much to begin with. They offer a rich ink flow for writing, despite being a fine nib. Are you interested if you have a pen body you're not using? I'm open to some price negotiation. I will ship them in a case.