If you are familiar with Sigma you know they carry amazing brushes in their collection, and with every purchase (over $30), you are gifted with a travel version of their Blending E25 brush. I love it when companies send you little gifts with your online order, because it really does show that they care about their clients and that they really do love sharing their products.
Their Blending E25 brush is one of my favorite eye brushes, so to receive one free travel version with every order is amazing.
It's an oval shaped brush that is fluffy and chiseled at the sides. It works amazingly at blending both powder and cream products onto your lids. I mainly use this to blend my eye shadow base (paint pots or other cream shadows), or blend out harsh lines. I also think it's small enough to use to deposit shadow on your outer corner for the smokey looks.
I have a few of these because of the Sigma orders I have made, but I also purchased a few full sized ones just because I love them so much (and I use them so often).