布小熊

They said:

A collection of assorted brushes made from natural and synthetic fibers that have been specifically chosen to achieve a flawless application by the every day woman and makeup artists. Invest in good quality tools for the most precise and flawless application.

I think it depends on which brush. Theoritically, synthetic are used for liquid and natural for powder.
I am thinking of getting a powder brush. The current one from a set I got few years ago feels very poky after a few washes.