Hakuhodo G5517 is an interesting eye shadow brush. It's round head is made of sculpted horse hair (1.7mm x 6.5mm). When I say "sculpted" I mean that it's not just pointy but also has a noticeable straight edge leading to the tip. Since Hakuhodo brushes are made of uncut hair this means that G5517 is carefully assembled to create this effect.
G5517 is relatively long and narrow (see comparisons to Shu Uemura 5R and Louise Young LY38).Horse hair is quite firm and has a distinct bounce and elasticity that make it a very impressive product-picker and excellent for smudging, especially if you find the Shu 5R too wimpy.
While Hakuhodo recommend G5517 also for blending, my personal preference is for softer, bigger, and fluffier brushes. Not that G5517 isn't soft: it's surprisingly lush and supple for horse hair, but it's kind of an overachiever when blending; however, it's excellent for a very quick smoky eye when you want precision in smudging to make sure pigment doesn't get all over the place.
Bottom Line: incredibly nice to have.
Hakuhodo G5517 Eye Shadow Brush ($20) is available from hakuhodousa.com. They ship worldwide.