Catalyst Polytip Bristle brushes are another Princeton breakthrough that advances the science of synthetic hair. This series is super stiff yet still extremely responsive. Unlike natural hog bristle, Catalyst has real integrity in water. Natural bristle can be rendered useless when it is water-soaked. The true advance in Catalyst is the Polytip feature. For the first time, the tip of each individual hair has been split to replicate the natural flags on the finest natural bristle. By giving each individual hair 2 to 3 distinct tips, Catalyst is able to hold a higher volume of paint while providing a smoother application. Designed for use with medium to heavy-bodied acrylics and oil paints, Catalyst pushes even heavy gel media with assurance. Catalyst Polytip Bristle brushes truly are tools that move paint.