As a teacher, these markers are a complete staple.  They provide a perfect line thickness for my classroom boards.  The color is dark and vibrant, the ink dries quickly, and the markers have little to no odor- allowing me to breathe easily in my poorly-ventilated classroom!  The ink erases well if erased shortly after using- but I have found that if you leave the ink sit on surfaces, it becomes more difficult to erase (and can actually require quite a bit of effort to remove).  Overall, a great product for my requirements.