Whether or not the barrel of the pen is translucent, allowing you to see the ink and filling mechanism inside.
How the cap is opened/closed from the barrel of the pen. Some common options include Snap-Cap, Screw-Cap, Magnetic Cap, or Capless (no cap).
Which ink this pen will accept. Choices include bottled ink and various styles of pre-filled ink cartridges.
Whether or not the cap fits securely onto the back of the barrel when open.
Whether or not the nib/tip can retract into the body of the pen (usually for click or twist-open style pens).
Measured from the place most people choose to rest their fingers, which varies with each pen.
The measurement from the back end of the barrel to the tip of the nib.
If a converter is included with the pen, this weight is reflected in the total.
If a converter is included with the pen, this weight is reflected in the total.