Ball joint dolls are an entire group of dolls, initially produced by several Japanese and Korean companies, but now being made world wide. They are made of heavy resin, strung with elastic, and utilize ball joints for a wide range of articulation. They are made to be customized, often coming unpainted and unfinished and their eyes and wigs are easily changed. They vary in size, but the largest are about 70cm tall and the smallest can easily fit in the palm of a hand. These are dolls (or just heads) which I was commissioned to paint, blush and sometimes "tattoo", or dolls in my personal collection.
You can view many more photos of these dolls as well as others I have painted in My Flickr Album.