It also depends on what type of coals you're using. If you're using a 33mm QL 11/2 - 2 should work just fine. If you are using a finger coal like Exotica, Stargate, Nours, Al Adjad (sp?), etc. You can get away with 1- 11/4-11/2" piece if you use a windcover. It all depends on the type of coal and the type of shisha. Some brands are heat sensitive and you have to experiment to find the perfect amount.