Princeton Catalyst Polytip, Brushes for Acrylic and Oil, Series 6400 Long Handle, Round, Size 4 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 round is a classic painting brush used for everything from flora and still lifes to portraits and landscapes  just about any subject matter in any style. Larger rounds can lay in large areas of color and stroke specific shapes, while smaller rounds are used for detail.