If you're looking to blend solid colors or something, I'm sure it's fine. I, however, tend to build colors on top of each other in gentle layers until I get the color and texture I'm looking for. If you take your work seriously and have a similar technique, do NOT use these blenders. It makes sense after the fact, but it will primarily blend the color you laid on the surface last, entirely changing your drawing. It also makes things much harder to erase, correct, or adjust (like trying to go back over it to fix the color). I would recommend doing many small drawing with different colors, techniques, and so on and then practicing with these blenders. Don't ever use this blender for the first time on a drawing you care deeply for or in which invested a lot of time. You will alter the drawing in ways you did not intend.
Keep in mind that this is basically clear wax that will smear the pigment sitting on the top of the page. If that doesn't sound okay with you, this is not the product for you. It might work well for many people, but it did not work out like I personally hoped.