Square nibs cut clean, architectural edges that transform lettering from curves into geometry. Speedball's A-style nibs excel at block letterforms, Gothic scripts, and decorative borders where precision matters more than flourish. The flat, squared tip delivers uniform line width across horizontal and vertical strokes, creating the crisp corners and consistent weight that define poster-style lettering and ornamental work.

Seven sizes span from A0 (widest) down to A6 (finest), with counterintuitive numbering, higher numbers mean narrower nibs. This range covers everything from bold headline letters to delicate border details within the same stylistic family. Each nib fits standard pen holders including Speedball's No. 9451, General's Cork Grip, Koh-I-Noor's No. 130N Crow Quill, and Speedball Classic series.

The square profile distinguishes these from rounded broad nibs or flexible pointed styles. You're working with hard edges and deliberate angles, ideal for Art Deco lettering, geometric patterns, and any application where letterforms need architectural clarity rather than calligraphic flow. Works with India ink, acrylic ink, and liquid watercolor.