Artists' brushes

Artists' brushes are usually given numbered sizes, although there is no exact standard for their physical dimensions.
From smallest to largest, the sizes are:
10/0, 7/0 (also written 0000000), 6/0, 5/0, 4/0, 000, 00, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 20, 22, 24, 25, 26, 28, 30. Brushes as fine as 30/0 are manufactured by major companies, but are not a common size. Sizes 000 to 20 are most common.
Artists' brushes are most commonly categorized by type and by shape.
Types include: watercolor brushes which are usually made of sable, synthetic sable or nylon; oil painting brushes which are usually made of sable or bristle; and acrylic brushes which are almost entirely nylon or synthetic. Turpentine or thinners used in oil painting can destroy some types of synthetic brushes. However, innovations in synthetic bristle technology have produced solvent resistant synthetic bristles suitable for use in all mediums. Natural hair, squirrel, badger or sable are used by watercolorists due to their superior ability to absorb and hold water.
Shapes are quite varied and often watercolor brushes come in the most variety of shapes. Rounds (pointed), flats, brights (shorter than flats) and filbert are the most common. Other shapes include stipplers (short, stubby rounds), deer-foot stipplers, liners (elongated rounds), daggers, scripts (highly elonged rounds), eggberts, fans, among others.
Bristles may be natural -- either soft hair or hog bristle -- or synthetic.
Soft hair brushes are made from Kolinsky sable or ox hair (sabeline); or more rarely, squirrel, pony, goat, or badger. Cheaper hair is sometimes called camel hair... but doesn't come from camels. Hog bristle (often called china bristle or Chunking bristle) is stiffer and stronger than soft hair. It may be bleached or unbleached. Synthetic bristles are made of special multi-diameter extruded nylon filament. Artists' brush handles are commonly wooden but can also be made of moulded plastic handles. Many mass-produced handles are made of unfinished raw wood; better quality handles are of seasoned hardwood. The wood is sealed and lacquered to give the handle a high-gloss, waterproof finish that reduces soiling and swelling.
Metal ferrules may be of aluminum, nickel, copper, or nickel-plated steel. Quill ferrules are also found: these give a different "feel" to the brush. The top of the range brushes, however, usually have ferrules made from transparent plastic tightened in place by thin wire.