What an excellent set of brushes, I would say some of the best I've bought in the last few years and I usually enjoy Mac ones. All the brushes are made of this extraordinarily soft and fine taklon bristles, which are of course synthetic. I find the buffing brush to be excellent for buffing in both mineral and liquid foundation. I am prone to having spots of dry skin and my previous buffing brush sometimes would bring that up and make it look more obvious, but this buffing brush is so soft and fine that it just blends the powder/liquid in so well while minimally disrupting the dry skin underneath, giving a very nice finish.
The next most useful brush is the contour brush. The size of the brush is excellent, not to big or small to get into the contour of the cheeks and the jawline. It makes for precise yet natural contouring but it would take a bit more time than say a slightly larger brush, which I am on the hunt for. A larger brush would be good for days that I am lazy and want a bigger splay of contouring in the back of the cheeks but this RT one is best, due to its size, for a slightly more precise contouring.
At first, I hardly found use for the detailing brush but now I hardly want to be without it. It is very small, soft and pointed and perfect for smudging out eyeliner. I use it to smudge out my Mac Fluidline as well as other pencil liners. The softness means that it hardly drags on the eyelids, which I found really surprising since the various smudgers I used to use always dragged more than this one. Also, I sometimes use it to put on brow powder when I want a softer finish than with my Mac angle brush, the larger one. I would suspect that this would be perfect for spot concealing but I hardly ever do that so I mostly use it for smudging.
The only brush I have absolutely no use for is the pointed foundation brush. It is way too small for me to ever want to use it for foundation and on top of that, I've never liked putting on foundation with a flat brush of that sort. I have used it for undereye concealing with good result, but nothing I couldn't do with my fingers.
Three out of four definitely is not bad considering that with most brush sets, there are bound to be brushes that I won't use. I am just very pleased with the quality of the three that I do enjoy. I think the design is quite good as well although I wish they didn't make the handles so thick especially on the larger brushes, since it takes up more room in the glass jar where I keep them upright.