In 1998, Bandai introduced the 1:60 Perfect Grade (PG) line. This line features extensive detail and articulation, light-up features, and a "body on frame" skeletal system in which the exterior panels of the model are separate components attached to a completely functional, articulated internal frame. This design element would later appear (sometimes in a limited form) in lower-grade models. The PG line is typically the most expensive among all Gunpla kits, and only a select few mobile suits have been released in this line.