A ball head is a metal or plastic apparatus placed on top of a tripod that increases stability and provides faster, more accurate rotation of the camera for the photographer. They are lighter than traditional three-way pan-tilt tripod heads.^{[citation needed]} With fewer parts and a much simpler mechanism, ball heads are usually preferred by more advanced photographers.^{[citation needed]} They are usually quite expensive – most professional-quality heads are more than US$200,^[1] although some heads are available for less than $100.