These are the Zig Cartoonist Mangaka Outline Pens made by Kuretake. Not sure why they are called Outline pens but these technical pens are more commonly referred to as multiliners or fineliners.
The pens are available in 5 different colours, namely black, sepia, light blue, violet and grey. They can be found sold individually as well as in sets.
The set that I bought comes with these three sizes: 01, 05 and 08. The smallest is a 003.
These are disposable felt tip pens so the tips will wear off with usage. If you use them on rough paper, they will wear off even faster.
Technical pens like this are meant to be used vertical. That way, the tip will be worn off consistently and will continue to give a uniform line. If you use the pens at an angle, then you will wear off the side of the tip, and chances are the next time you use the pen, you won't be using that exact side that's worn off, hence the line width you get will be slightly different from the last time you use. That's just how felt tip technical pens work.
The pen widths are also labeled on the body. The body by the way is just plastic, much like Copic Multiliners.
The cap has a metal clip unlike the Copic.
The pen used water-based pigment ink. Since they are pigmented, they are supposed to be waterproof when dry, and lightfast.
Here are the strokes as drawn on lousy paper. Both the Zig Cartoonist Mangaka and Copic Multiliner feather and bleed when the tip is placed on the paper surface for a period of time. The paper that you use matters.
This sketch above was drawn on better quality paper. There's no feathering and bleeding. The ink is retained on the surface. The ink dries fast and is waterproof so you can use other water-based media over it.
With the three line widths, you can get the pens to create depth. For example, in the sketch above, for subjects in the background, I used the thinnest lines and the subjects in the foreground were drawn with the thickest line. The difference between the line widths are discernible when placed side by side, and when used like this it creates an illusion of depth and perspective. Architectures may also use thin and thick lines to differentiate form of buildings.
Overall, the drawing performance of Kuretake's Zig Cartoonist Mangaka Outline pens is similar to many other multiliners or fineliners that I've used. All I can say is, they perform well as drawing pens.
As for whether they are worth it or not, it will depend on the price they are sold as. They are usually sold around USD $2. These pens are not refillable by the way.
If you want a detailed comparison with other multiliner/fineliner, check out this review at http://www.parkablogs.com/picture/fine-liner-pen-shootout-%E2%80%93-comp...