Ball head
A ball head is a metal or plastic apparatus placed on top of a tripod that increases stability and provides faster, more accurate rotation for the photographer. They are also lighter than traditional three-way pan-tilt tripod heads. With fewer parts and a much simpler mechanism, ball heads are usually preferred by more advanced photographers. However, they are usually quite expensive due to the precision-made pieces inside and the detailed finish outside – most professional-quality heads are more than $200 USD,[1] although some heads are available for less than $100.
See also
Wikimedia Commons has media related to Ball heads.