Gundam Decal (GD) (ガンダムデカールGandamu Dekāru?) is a line of water slide decal sheets for Gunpla kits from the Gundam meta series. These sheets serve to either replace existing marking sheets or add extra detail to Gunpla kits.
There are several different sheets, each made for the Gundam kit that is specified. Be sure to get the right one for your kit!