The Astonishing Nails Gel Brushes are made with the highest quality of Kolinsky Sable Hair. The bristles are secured with an Epoxy Resin to prevent shedding of the hair. The #4 Gel Brush is a size four square brush. The brushes are designed for creating the perfect smile line with Astonishing Nails Gels, building your complete nail, fill and backfill maintenance. Brushes can be cleaned with Astonishing Nails UV Cleanser. This brush can be used with any Professional Gel System.