On Amazon it's stated these are best used for Adult Coloring Books, which may very well be the case. The paper that makes up these coloring books may have a toothier paper surface the lead adheres to better than, let's say, smooth like I tested. I wouldn't know because I don't have a coloring book to try these out on.
One review that stood out to me was the fact they are light in color value and was not satisfactory to that person. I don't recall if that individual shared what paper they tried their pencil leads on.
Being the person I am......curious and liking to experiment, I purchased a set.
That person is indeed right, although you can go dark if enough force is applied when laying down color. That would quickly become cumbersome though, I'm sure, for most people.
This little example was done in a PaperBlank's journal which has a slick/smooth paper surface.
I've included on the example my own thoughts and personal findings. Personally they are nothing more than colored pencils in a format to fit a mechanical pencil. Great for making up a small sketch kit without having to take a tin of regular sized color pencils; BUT, definitely too much work would have to go into obtaining darker values for my liking.
I've been on the hunt for tinted "graphite" that behaves like regular graphite one can smudge and blend with a tortillion or paper stump. These definitely do not fit that bill.
I have a set of Koh-I-Noor Gioconda 5.6mm Artists Drawing leads on order and can't wait to try them out. They come in a set of six (browns/sepias, black, and white). Will share my findings once I've received and had a chance to try them out :-)