Sketch Markers
The Sketch Markers are refillable and change the tips, have exactly the same ink and the same quality. The differences are:

a) The number of colors available in each model:
Sketch has all 358 colors of Copic’s palette.
The Classic is available in “only” 214 of these colors.
Ciao is available in “only” 180 of these colors.
Still, you can buy an empty pen (without ink) and refill it with any other refill color, in case you find an indispensable color. Or you can mix different refills and create your own color.

b) On the types of tips available for each model:
The Sketch and Ciao have 2 tips each, one being a medium size bevel and the other a brush, called the Super Brush. The tips of these two models are absolutely identical. There is also a third tip option that is rounded (called medium round), which also fits these models and is sold separately.
The Classic also has 2 tips, a large beveled tip and a thin, hard tip. Classic also has several other models of spare styli (sold separately) for creating countless strokes.
Wide has only one end, a huge beveled 2 cm wide, and a straight base end for calligraphy (sold separately) is also available.
Note: Except for the Sketch and Ciao models, the nibs are not compatible between the different pen models.

c) The amount of ink that comes with the pen:

Wide is the one with the most ink, approximately 4ml.
Classic comes second, with approximately 3.2ml.

The Sketch has 30% less than the Classic, i.e. approximately 2.5ml.
And finally the Ciao, has 30% less than the Sketch, that is, approximately 1.6ml.

d) Airbrush compatibility:
Only the Sketch and Classic models are compatible with the Copic Airbrush.

e) In the profile of the plastic body:
The Sketch and Wide models have an oval profile.
The Classic model has a square profile.
The Ciao model has a cylindrical profile.

f) On the markings on the pen body and cap:
Only the Sketch, Classic and Wide have the name and color number on the top of the pen cap, making it easy to identify when they are upright. All models also have markings on the body.