1.) These are the meanings of the letters in the brush names including the letters P, PH, or PS: P: This is a standard classification. A "P" brush is a basic brush. PH: This is a "hard" brush. This kind of brush has great resilience and is good for eyeliner. PS: This is a "soft" brush. This kind of brush is best for painting and nail art. 2.) This is the meaning of the "6" and the following letters in certain pro series brushes: "6" is the length of the circumference of the head of the brush. The S/M/L indicates the length of the bristles in the brush. 3.) The pro series brushes were developed especially for use in body and nail art. When artists use brushes made with weasel hair, it takes more time when using a brush made from weasel because of the need to dry the animal hair before each different use (color, etc.). With this new product, however, an artist can quickly and effectively apply paint and make up. This means (for example for movie special effects) that these brushes are very helpful for when you usually need to change the brush each time it is used.