This is one of my favourite Hakuhodo blush brushes. Almost all of my brushes are the S100 series (vermillion handles with 18 ct gold ferrule). I also have some 200 series plus G/K (the S100 series are all natural hairs so if you want a good concealer brush, lip brush, cream/liquid foundation etc you need to look at another series).
The hairs on the S110 are slightly longer and are not as dense as the popular 210 brush. Both are made of goat hair but the 210 is by far more dense which makes the 210 better for buffing mineral powders or sheerer cheek colour products.
The S110 is not as dense and I like to use this more for standard to heavily-pigmented blushes (Nars, Chantecaille, Dior, Burberry, Chanel Joues Contraste etc). If you want a blush brush then I would highly recommend sticking to goat hair as the blue squirrel brushes are extremely soft - so much so that they really are only ideal for finishing powders or highlighting powders. Blue squirrel hair just doesn't have the ability to pick up a lot of product. I find the hairs to be very fine - they really suffer if use a squirrel hair brush on my cheeks before my skin has sufficiently dried form my foundation application.