有兩個原因，一是鏤空型，容易變形，不易成圓。二是實體型，小單位的組件沒有折好。

來源: 三月的天空於 2011-01-03 23:40:13 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

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