Important things for violin bow
The shaft, or say stick. First is the material, second is the shape. Pernambuco is better than normal Brazilwood, while carbon fiber is better than fiberglass. Too stiff or too soft are both not good thing for a bow. We don't get too deep and make it become a physics subject, just knowing what kind of stick material is better will be fine.
Let's continue to talk about the shape. The shape is decided mostly by craftsmanship, a good maker can produce a straight stick with a beautiful camber just perfect for bowing, it can be made by hands, and can been seen just with eyes. If you are looking at a composite bow, it must be straight and with a beautiful camber without doubt.
The frog, mostly made of ebony, which is from a lot of different species of "black wood", while some "plastic" frogs also being used by some brands. We don't know if plastic frogs are better than ebony, but plastic are always cheaper as we know. Ebony have a lot of grades, mostly can be told by appearance, if it feels well and natural, if the surfaces are smooth. It's easy to tell the differences if you have different frogs brought to your face, it's just what we do everyday. 
The Frog + Button (Screw), usually it's not a problem, but it's different if they fit together tight and smooth. That'll make a more endurable hair adjusting mechanism, and feels better while you loosing and tightening the hair.
The Bow Hair, we only talk about natural horse hair, often it's not a problem that you see a pale yellow horse hair, it's natural. You'll find our better and higher quality bow's hair changes color slightly from pale yellow to white from one end to another on some bows, it means the hair is not bleached at all. Mostly bow maker use hair from a male horse, because male horse-tail don't get wet with their own urine. We buy Siberian, Mongolian horse hairs, they are the best to make a bow, and we use several grades of them. By the way, the hair are easier to get pulled apart after bleached. Some player need a coarser hair, maybe black hair on a double bass, or cello bow, please let us know.
