Hakuhodo Kokutan series offers quite a few options for eye shadow brushes. Last year I added the two larger ones to my collection: Kokutan Eye Shadow Brushes L and M. Both are made of blue squirrel hair (and the typical ebony handle of Hakuhodo's Kokutan line); their dimensions:
M is 14mm x 5mm x 15mm
L is 27mm x 9.4mm x 15.7mm
As you can see, Kokutan M is a pretty typical wide all-over eye shadow brush for applying a wash of color and blending it over the lid, while Kokutan L is a massive blending brush. It's so big that it can easily be used as a highlighter brush, powder bush and perhaps even for contouring. Both brushes are wonderfully soft, but since they're packed densely they offer enough resistance to perform well.
Big and wide blending brushes aren't necessarily an everyday tool. Often you only need to blend from the crease out/upwards, so a more directional brush is better. Also, if you have relatively small eyes or limited lid space Kokutan Brush L will not fit. Its more than twice the size of Paula Dorf's Eye Blender which was my widest blending brush until I got this Hakuhodo. I use it to give one last blending stroke, but I admit that even for me it's more of a face brush-- a really good one, mind you, as the size and hair quality are perfect. Kokutan M sees a lot more action, though. It's an excellent tool, as hard working and sturdy as it is luxurious. It applies color and diffuse it to perfection, and as long as the size works for you this is good buy.
Bottom Line: Skip the L unless you're after a small face brush.
Hakuhodo Kokutan Eye Shadow Brushes L ($64) and M ($50) are available from hakuhodousa.com. They ship all over the world.