I bought 4 brushes from FO series, because I wanted something soft "like squirel", but did not want to loose the product pickup ability to the extend that squirrel hair does. I have Z-8 cheek brush and I love the softness of it, but I find myself sometimes wondering "where the colour is".. So I tried the fox hair to see whether it is a better match for my needs.. aaaand it is.. :) It is still very soft hair and nice on the skin and it has better ability to pickup the product. If I compare FO-3 and FO-4 (cheek brushes), I would say that the angled FO-4 has stronger pushback and gives you more precision whereas the FO-3 is slightly bigger, definitely feels fluffier/more airy and is less precise with the application. Both are very nice, both give wonderful blended look to the cheeks.. it is really up to one's preferences.. What I want to mention though is that the handles are very light in weight. These brushes are "head heavy". I prefer a bit more weighted handle, since it somehow feels more luxurious to me (again it is up to preference). Anyway I do not think about it really anymore, I just pick up the brush, fluff it on my cheeks and enjoy the look. If you are eyeing FO brushes, I would say give it go. I definitely do not regret buying them.