These technical pen sets come packed in convenient flat-shaped, hinged-lid plastic cases with a push-button release. Each set includes a 3/4 oz. bottle of black Universal drawing ink and nib keys. The 3-Pen Set includes line widths of 3x0, 0 and 1. The 4-Pen Set includes line widths of 2x0, 0, 1 and 2. The 7-Pen Set includes line widths of 3x0, 2x0, 0, 1, 2, 3 and 4.