Kolinsky sable is the premium natural hair used in the best miniature brushes. The hairs taper naturally and carry a large paint reservoir in the belly while snapping back to a needle point — a combination synthetics still chase.
A good Kolinsky round in size 1 or 2 does nearly everything on a miniature, from base coats to eyes. Care is the price of entry: rinse before paint reaches the ferrule, reshape the point, store tip-up, and never leave it standing in water.
See it in context in our brush painting guides, or explore the tools hands-on in The Bench.