Varnish and enamel brush. Satin-edge Nylox and Orel polyester filaments. XL brushes are highly recommended for both interior and exterior painting projects with all paints. The stiffness retention of XL brushes makes them especially high-performing for outside painting under hot and humid climate conditions. Each XL brush style has its own unique hand chiseled formulation for maximum paint lift and smooth, no-drag application.