Princeton Catalyst Polytip, Brushes for Acrylic and Oil, Series 6400 Long Handle, Flat, Size 12 Polytip Bristle brushes are another Princeton breakthrough that advances the science of synthetic hair Tip of each individual hair has been split to replicate the natural flags on the finest natural bristle Holds a higher volume of paint while providing a smoother application Designed for use with medium to heavy-bodied acrylics and oil paints The flat and flat shader is composed of medium-length bristles that taper to a chisel edge, allowing for a wide range of applications. A good-quality flat will have spring and will snap back to shape when bent gently. A flat can apply broad strokes or a fine line, when used on the chisel edge.