In 1990, Bandai introduced the High Grade (HG) line, which began an ongoing process of increasing model quality, and the creation of a grade system to describe the detail and quality of each kit. HG kits had much higher detail and articulation, as well as features normally found in larger-scale models, despite being 1:144 scale. One example is the 'Gundam Core Block System', in which the pilot sits in a "Core" which can be removed from the Gundam to become a distinct vehicle, and the Zeta Gundam 's transformation feature.