Reserva 1214 Travel Round Size 10 has a brush head that measures about 5.7mm Diameter x 25mm Long. Kolinsky-Tajmyr Sable is 100% male Kolinky sable, is sourced from Tajmyr region in northern Siberia, is considered the elite hair for watercolor, points perfectly and has an extraordinary capacity to retain liquids. 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.