From the Mack Brush Website:
Our choice of hair for this brush was China Blue Squirrel Hair. Synthetic detail brushes are no comparison to the natural hair and pointed detail brush of the new Micro Script brush. You will get the finest little lines and delicate touches you didn’t even believe were possible. It is the brush you will fall in love with for all the little things you do.
Available in sizes 3/0, 2/0, 0, 1 & 2