Chinese Communist insignia, suitable for the Korean War through to the present day. (Minor variations exist, but this depicts what seems to be the most common.)
These decals are scaled to represent 30", 36" and 48" high markings in 1/300 scale. (They're also ideal for large aircraft in 1/600; equivalent to 60", 72" and 96" high. ) The actual heights are 2.5mm, 3mm and 4mm - width is just over double that.