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The MAC 168 ($35) is not as dense as the Sonia Kashuk Multi Purpose brush, but it`s by no means floppy for blush or bronzer application. However, I do find it too flimsy for contouring. I prefer a firmer and smaller brush, such as the Mac 109, for contouring. I use the Mac 168 mainly to apply regular pigmented (not sheer or highly pigmented) blushers, such as my Dior DiorSkin Nude Healthy Glow Powder bronzer.
The bristles of the MAC 168 are not as soft as the Sonia Kashuk Multi Purpose brush, but it`s not as prickly as the Sephora #40 brush. The only gripe I have about the MAC 168 is that it sheds like 1-2 hairs each time after I wash it. Maybe I got a defective one?
The Sonia Kashuk Multi Purpose brush ($17.99) is denser and much softer than the MAC 168. I had trouble finding the right brush to apply my Too Faced Peach Leopard Bronzer because the product is super sheer. The Sonia Kashuk brush works well with Peach Leopard because the brush is dense enough to pick up the color in the pan. This is definitely a must-have for applying sheer products.