We didn't have a fourth player for some time so we switched from riichi to three player version with korean\japanese rules as described on Wiki (I guess that's the most popular version for 3 players).
But description on that Wiki page seems not that clear compared to riichi. The question here is about
5 bamboo tiles, in Recap is says:
2-8 of bamboo is removed from the game with the option of using two 5 bamboo pieces which can only be used as a pair (which when successful scores many points).
Well, the only two hands I see with them are half-limit
Little Jade Dragon and full limit
Pong of 1 and 9 bamboo and pair of 5 bamboo. Is that all? They are not mentioned in common hands there nor in scoring, and not used even in 13 orphans. Is some info missing there or is it just as intended? Because it seams too little for rarest pair in set, in my opinion.