Escoda Optimo 2813 Oil & Acrylic Kolinsky Sable Paint Brush Filbert; Size 1 Optimo 2813 Filbert Size 1 has a brush head that measures about 1.66mm Wide x 8mm Long Kolinsky sable filament is a perfectly balanced combination of male and female hairs, is well regarded for it's softness and natural spring and used with watercolor, oil and acrylic paints with equally positive results Escoda brushes boast trademarked tripled crimped ferrule ensuring a lifetime secure fit, unique curing process that locks each hair in place creating a permanent brush shape and all wooden handles are ergonomially designed and made from the finest brich wood available Escoda's ISO 9001/100 Cerification ensures that each brush is engineered and hand crafted to exacting standards and is supported by Escoda's Lifetime Guarantee against workmanship defect if purchased from an authorized dealer Since fine art brushes are hand crafted, please expect some variation to the listed dimensions