This is a Kaweco fountain pen nib replacement unit. I purchased it for 42,900 yen. The product number is kaweco-fp09, and according to the website, it is compatible with the following: AL Sport, AL Sport AL, AL Sport Stone Wash, Special, Steel Sport, Student, AC Sport, DIA, Brass Sport, Liliput I used it with a Brass Sport. Therefore, compatibility and suitability for other models are unknown, so please check before purchasing. I attached it once after it arrived and tried writing with it, but the line width was finer than I expected, so I am selling it. It's finer for a B nib, and I think it's slightly thicker than an M or equivalent to an M. I will ship it in the included tin case with water protection. Kaweco Kaweco kaweco Nib Nib replacement unit Nib replacement unit Brass Sport Kaweco Sport Fountain pen 14K 14 karat Bicolor B nib Bold