Premium 100% Synthetic :This Staalmeester® round brush has 100% synthetic fibers, a stainless steel ferrule and a strong wooden handle. It is beautifully constructed to last you through many projects. This is PERFECT for applying Fusion !!!! The synthetic fiber resists water based paint and are soft and supple which results in a smooth finish. Please note the binding string for these are green and are to be kept intact to keep perfect bristle tension and alignment.