Sizes – How big will your pen be compared to other brands?
Steps – That little shoulder on the barrel is called a step. See examples here.
Clips & Roll Stops – A few steel options and almost limitless custom options in silver and gold…
Materials – Acrylic, Alumilite, Ebonite
Nibs – Tips, materials
Filling – Converter, Button, Bulb, Piston
Section Shapes – Straight or pinched?
End Shapes – Flat, round, pointy?
Ink Windows – Do you want to see how much ink is left?