Chinese bristle brushes are famous for the quality of their pig bristle. Bristles of varied diameters are used depending on the recommended type of work.
The conical brush is for trim painting and sign painting. The taper of the bristles (not achievable with extruded man-made fibers) ensures the paint will flow to the brush tip. Surface tension of the liquid causes it to naturally migrate toward the smaller end of the bristle.
To create the stiffness required in a trim brush, both coarse bristles (0.08mm to 0.14mm) and fine bristles (0.04mm to 0.06mm) are used. It is far better for controlled paint application than a flat brush.
For the fan brushes (which are used for furniture finishes) fineness of fiber is important for smoothness of finish, so only fine bristles are used. The fan tip adds an element of flow control that a square tip cannot replicate. The paddle-style handle looks odd but is actually more comfortable in this use than the Western style of handle.
Both brush styles are well made with hardwood handles, nickel-plated brass ferrules and all natural bristles.