On its own this is a really great eye/crease blender brush with just the right shape to get into the crease and be able to blend well/smoothly/evenly. The denseness and "resistance" are just right. A great product at a great price.
To compare it to the MAC 217, for which it is a dupe:
The Sigma one is about a half inch or so longer at the handle, and the brush part is a bit longer as well. The sigma brush is not quite as dense as the MAC one (close though). The MAC 217 still blends better because of the thicker overall denseness & thickness of its bristles...so I still prefer it. .BUT the Sigma is pretty darn close. It's the best dupe I have seen yet (and honestly there really aren't any other that come close IMO)...and I know I am going to get a LOT of use out of it.