Sigma F40 is their large angled contour brush, it has white goat hair. It can be used to apply blush (which I would use it for) or bronzer. This is a dupe of the MAC 168. It's as soft as everyone says it is.
Sigma E50 is the large fluff eyeshadow brush. This baby is huge, it can cover my entire eyelid. This can be used for a wash of colour on your lids. This is comparable to the MAC 227. My first impression of this brush is that it sheds hair like a monster! I hope this dies down after I wash it, or else I may be contacting Sigma regarding this. I haven't washed it yet, just touching the bristles and examining it, I keep pulling out hairs, probably like 10-20 already.
Sigma F75 is their concealer brush, it is tapered and has orange synthetic hair. It can be used for placing and blending concealer on the face. I will probably use it to tap concealer under the eyes. It's a nice size, I wish it were a bit firmer, but it's okay, good for delicate areas. It's a dupe for the MAC 195, looks completely identical to it.
Sigma E35 is the tapered blending brush. It's made of goat hair and can be used for blending eyeshadow or blending in concealer under the eyes (which I will probably use it for). It's very soft, however the bristles are much more fluffy than the MAC 222 (which this is a dupe of). This is like a longer version of the Sigma E25. This reminds me of a white MAC 224 brush moreso. With this brush, Sigma did not get this brush dupe quite right in my opinion.
Sigma E45 is a small tapered blending brush for eyes. This can be used for placing eyeshadow in the crease and blending it. I was surprised how pointy and precise this brush is, it is really well made. This is a dupe of the MAC 226 which was limited edition and is not available anymore. I don't have that brush, but judging from pictures, this Sigma one seems a lot more pointy.
Do you have any of these brushes? Which ones are you planning to get?