The Eclipse Range is 100% Synthetic, Vegan Friendly. They are great for Oils, Gouache, Acrylics, and Watermixable Oils. The Eclipse is a synthetic mongoose that is stiffer than sable, yet softer than bristle. This long filbert has extra length as requested, allowing more flexibility. It should also allow you to keep the paint away from the ferrule of the brush, which in theory should make it easier to clean. A favourite for portrait painters – and lovers of filberts!