One of every 1, every 9 and every honour, plus a duplicate.
One of each terminal and honour, thirteen distinct tiles, plus a second copy of any one of them. That is 1 and 9 of each suit, all four winds and all three dragons. It is a limit hand, and it is the only hand with no sets and no ordinary pair structure.
It is an opening-hand decision. Ten or eleven of the thirteen at the deal makes it realistic; below that it is a trap that costs you every other hand. The wait is unusually wide at the end, because any of the thirteen kinds you are missing completes it.
Chasing it from a mediocre start. Every tile you keep for it is useless for anything else, so a failed attempt is a hand with no fallback at all. This is the most expensive wrong commitment on the board.
Nothing adds to it, and nothing needs to. It is concealed by nature. Its one unique privilege is that it may rob a concealed kong, which no other hand may do, because it is built from single tiles.
Which tile do I need two of?
Any one of the thirteen. The pair can be formed from whichever you draw a second copy of.
Can I really rob a concealed kong?
Yes, and only this hand can. The rule exists because the hand needs single tiles that would otherwise be locked inside a kong.
Is it worth chasing from eight tiles?
No. From eight you are five specific tiles away with no fallback. Play an ordinary hand.
Play Mahjong Winds
Every win shows its faan line by line, using the table on this page.