Kolinsky Sable is the best hair available for the manufacture of artist brushes due to being conical in shape, strong in character with a long, tapered point and thick belly. 

Rosmary & Co Series 33s are one of the most popular watercolour brushes they make, and have been adopted by hobbyists as one of the premier brushes to use. They are a great all-rounder, with an excellent point, and great pigment and water carrying capacity. Rosmary & Co describe them as the Rolls-Royce of brushes. Kolinsky Sable hair is the best money can buy.

The Series 33 work well in watercolours, inks, oils for details, acrylics and for botanical painters alike, though they are favoured by watercolourists.