I am a geology masters student and with mapping and cross-sections colouring can be vital to my degree coursework. I've found these colouring pencils to be excellent, the pencil leads have never broken and they colour smoothly and evenly. The triangular shape and rubber coating also makes them very comfortable to use, even when using them over a period of several hours. The case is one of the best features as allows the pencils to stand up, which makes it much easier to swap colours when using them, but also protects them during transport. I keep mine in my bag daily and have travelled with them all over Europe on field trips, but they have never broken.
I have tried many different makes of colouring pencil but these are by far the best I have used.