(a well-known manufacturer in the "12-inch" figure hobby) and the naming conventions of their "Heidy" or female-focused head sculpt series, here is a professional-grade write-up for this model. Product Overview: TTL HeidyModel-006 HeidyModel-006
The term here refers specifically to the internal joint system. The HeidyModel-006 features the "V.3 Articulated Endoskeleton."