Do gradation with only one pen.
Colourless blender will not stain other colours.
Fun experimenting on the mixing.
Takes a bit of time to figure out which side is the mixing chamber and brush nib, so might not be suitable for professionals who want to work fast.
Lighter tone only last for a small area, not suitable for covering large area of pale tones.
Outliner pen provided too thin for my usage. But can be compensated with other marker pens.
I would say the markers are great for people doing occasional illustrations and small drawings, in which getting the exact colour is not crucial and is fun to discover what you will get. However, if you need to work fast and exact like product designers and fashion designers, you might want to stick to regular markers.
To buy visit: http://www.chameleonpens.com