Optimo 2913 Bright Size 4 has a brush head that measures about 3.87mm 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