Number of tiers

Constitution of Comoros (2000, with amendments up to 2009) 

https://www.constituteproject.org/constitution/Comoros_2009.pdf

20: The Assembly of the Union shall be composed of twenty-four (24) representatives of the nation elected by universal suffrage in single-member constituencies on the basis of majority voting in two rounds; (and) representatives of the autonomous islands appointed by the Island Councils from among their ranks, at the number of three (3) for each autonomous island.