Korean Flower Card Game / Hwatu / Go-Stop / Godori
The Korean game played with these cards is more often referred to as Godori, or Go-stop.
The Hwa-tu cards are approximately 1 3/8" wide by 2 1/8" high and are smaller and thicker than playing cards used in the West.
The face of these plastic cards is glossy, while their back is often rough, with a texture in relief, to prevent them from slipping while held in a hand or from sliding on the table.
Hwa-tu makes a satisfying "snap" sound when thrown down with vigor.