#006 : Cylinder behind the skull [T1 Endoskeleton ball joint,T2 Endoskeleton universal joint]
It seems that ball joint is used for T1Endoskeleton and the universal joint was used for T2 Endoskeleton.The Animatronic Bust from T-STUDIO uses a ball joint connector in accordance with the T-800 in the factory from the original movie.
