Tachikawa Comic Pen Nib Holder for Various Pen Nib - Model 25. Pen body only, different nib styles are available separately. This holder is compatible with both regular and round nibs. The holder features special double rubber rings at the tip, the inner ring can take smaller round nibs and the larger ring can take regular nibs. The rubber grabs the nibs tightly, preventing shifting when drawing.They are great for creating detail in drawings. Varying nib sizes are available to suit your drawing needs.