Just got in mail today these little babies from Sigma. Haven't used them yet, but will say that they are high quality brushes and feel solid in hand. I got new sythetic angled brush F87 and a duo-fibre blending F50 (a dupe for Mac's 187). As a bonus, I also received a blending brush E25.
I haven't tried them out yet, but I love the density of synthetic brush F84. Well worth $16 price tag.