Flat Cow Hair Brushes. The classic Waldorf school brush with a natural handle and soft cow hair. With proper care these brushes will last for a long time. For the lower classes, we recommend sizes 16, 18, or 20 and for kindergarten, sizes 20 or 22. No. 22. Width: 22 mm, length: 32 cm (width: 0.87 inch, length: 12.6 inch).