Real Grade kits or RG as the moniker on the box indicates, are fairly new to the Gunpla community.
Introduced in 2010, in celebration of the 30th Anniversary, RG kits focus between the skeletal inner frame of Master Grade's, and the size of an HG (1/144).
RG kits have more detail, like color separation, and articulation to give a more realistic approach; they also come with a hefty number of decals .
RG kits are great for builders who want to keep within the HG size but want more out of their kit.
Within recent years, RG units like the Nu Gundam or the Sazabi have been noticed by the community and praised for their excellence.
