Just to share about the most common cap in my country, Indonesia. There's a very short article in wikipedia: http://en.wikipedia.org/wiki/Peci I just want to add a bit. Although it is somewhat stated as "national" cap, being a country with the biggest Moslem population, it is automatically identical with "Moslem wear". (I'm a Christian BTW). I ain't gonna wear it certainly. But in the cities, big cities particularly, very rarely people (especially youth) would wear peci, unless they are attending formal occasion, especially religious ones, going to mosque, or Moslem wedding ceremonies. In the villages it is more commonly used. Govt. officials on formal occasions sometimes wear this "national cap" especially during their inaugurations. Ministers and presidents. But female officials need not wear it - it's not a unisex cap Black peci is the most formal color, but plenty of variations also available, with various patterns, but still more related to Moslem headwear. Sometimes it is called "Songkok" or "Kopiah". In terms of structure, I guess it somewhat resembles military cap, air force usually - I don't know what you call it? So you can flatten it for use and "open" it when you want to wear it.