This is a very well designed concealer brush. It's shaped flat and slanted almost mimicking the tip of a finger which is perfect for under eye concealing. The best way to apply concealer under the eyes is a patting motion. With my finger, it takes forever and sometimes depending on the product, it applies unevenly. With a brush, sometimes you sweep the product away too much. This does a wonderful job patting the product onto the skin, you use less product and less time. It doesn't matter if the consistency of the concealer is thick or thin, just do a patting motion and it spreads very well. It also fits very well on the inner corners of your eye which is sometimes hard to conceal without getting too much product in the crease, esp. If you have deep set eyes.
Normally I refuse to spend a lot of money for synthetic brushes since most of the time they are made in china. No offense, I come from china myself, we have a lot of great products for less money. But I bought 2 because this is just the perfect shape, perfect density. With its shiney packaging I thought it would feel cheap but it isn't, it has good weight to it and a good feel. The letterings are very classy and expensive looking. You really have to feel and use the brush to appreciate it and that's why I decided to purchase this.
I have not used this with concealing other blemishes on my face because for covering pimples, I think a tiny concealer brush works best unless you are covering up something as big as the tip of your finger.
For reference, I've used this with the Marc Jacobs remarkable concealer and maybelline age rewind dark circle eraser.