Brushes come in a variety of shapes and sizes, and brush sizes can differ between manufacturers. This article explains brush numbering systems that appear on the handle of paintbrushes.
Chaos Cards Sable's Kolinsky brush set. : r/minipainting
Jackson's - Watercolour Catalogue - 2015 by Jackson's Art Supplies - Issuu
Hero Arts Blog Hop: Spring Catalog {creative chick}
Understanding Brush Sizing Systems - Jackson's Art Blog
Princeton Brushes for Oil, Acrylic, and Watercolour - Jackson's Art Blog
Jackson's Flat Studio Synthetic watercolour brushes are excellent quality and useful for producing a variety of watercolour techniques.
Jackson's : Studio Synthetic Watercolour Brush : Flat : Size 3/4
Jackson's : Studio Synthetic Watercolour Brush : Rigger : Size 4
Da Vinci Kolinsky Sable : Series 1203K : Ultra Fine Liner : Size 6
Understanding Brush Sizing Systems - Jackson's Art Blog
Art Brushes: Natural & Synthetic Hair