These can include different tapers to the pen caps and bodies:
Different end shapes such as round (semicircle), cone, flat, and rounded:
Different colored finials on the ends of the pen cap or body, as well as color bands (no metal bands) where the cap and body screw together:
Furniture: metal bands in brass, bronze, nickel silver, and aluminum. Clips in gold, silver, or a variety of other finishes, depending on the model and market availability. However, over time clips can lose their spring, be bent, and even mark the cap of the pen. Supply for clips is also variable. As an alternative, I include a leather scabbard for each pen in black, tan, or brown leather providing suitable and portable protection for your pen.
Pen Size - Pens are offered in three lengths: Small (5 ½' - 5 ¾), Medium (6"), and Large (6 ¼"); widths vary from 14.5mm to 16.5mm at the base of the tenon of the pen body just behind the threads; caps can always be wider than the pen body. Pens can also be made oversize in length and width depending on your desires. The pen cap and pen body can be different colors from each other, as can the section holding the nib. Sections can be 18mm to 22mm in length.