Amazon.com: Rotring S0699380 Isograph Technical Drawing Pens, Set, 3-Pen College Set (.25-50 mm), Brown : Everything Else
Rotring 400 Cartridges Fountain Pen in Silver with steel nib (selection) | eBay
Rotring 600 3-in-1 Multicolor Pen and Mechanical Pencil, Switches Between 2 Ballpoint Pen Fine Point Tips (Black and Red Ink) and 1 Mechanical Pencil Tip (0.5mm Lead), Black Barrel
Amazon.com: rOtring S0699370 Isograph Technical Drawing Pens, Set, 3-Pen College Set (.20-.50 mm),Brown : Everything Else