The #6 Bristle Filbert Brush is used most commonly for the seascapes and can also be used for tree trunks and other small detail work. The Bob Ross landscape brushes are special brushes made from a blend of natural and synthetic bristles and shaped according to Bob's very precise specifications for the Bob Ross Wet-on-Wet TechniqueΑΌ. Remember, ordinary brushes are not the same and can't create the same beautiful effects these will.