Big four winds
Pungs or kongs of East, South, West and North plus any pair. Some riichi rules count it as a double yakuman, and MCR values it at 88 points.
Little four winds
Three wind pungs and a pair of the fourth wind, plus another set. A limit hand in many styles.
Spotting it
Exposed wind pungs make the hand visible. When an opponent has two or three wind pungs showing, the remaining winds are dangerous discards.
Rarity
Wind tiles are scattered and only four copies exist, so assembling all four sets is extremely unusual.
