212 Synthetic Flat Definer Brush For All Formulas, Flat-Shaped, Defines Eyes For lining and defining the eye with colour. The firmly bristled, flat shape applies colour in a stroke to provide instant definition. Use with powder, liquid or cream products. Made of synthetic fibres. M·A·C professional brushes are hand-sculpted and assembled using the finest quality materials. They feature wood handles and nickel-plated brass ferrules.