The colours in the set I bought are a nice selection:
They (as expected) have both vibrant colours and a fine line. Here are the colours written out on ~A6 Clairefontaine paper, which shows off their colours well (and after all, I am mostly using Clairefontaine in my bullet journalling).
The case is a strange thing. I find the catch to open it very stiff (and on a couple of occasions have jemmied it open with a ruler). Once it's open, it can be folded back on itself so that the top and the base are now in contact and then you can keep rotating the two bits and open it out and the pens are now on the other sides.
|Back to back|
|Opened - with the two sides swapped|
While this is quite fun, I do find getting the pens in and out of the case difficult as the clips for the pens are quite firm. It also takes up a lot of real-estate and so I've transferred all of the pens into my pencil case. The case they came in is okay, but it's too bulky and stiff for my taste. However, the pens were the cheapest in this form!
I'm using them for colour-coding the to-do/next actions in my journal/planner, but if you have been bitten by the adult colouring books craze, they would be fabulous as the ink flows well, the tip is very fine and the colours are generally strong.
All in all, I think they were a good purchase and have helped with the colour-coding in my bullet journal.
[If you buy them from the link below, I get a few pennies.]