String button envelope from the Japanese manufacturer SIWA. The material "Naoron" is a very flexible, tear-resistant, and water-repellent paper that remains soft and foldable. It is made from wood pulp and polyolefin using the Washi-Suki process. Objects made from Naoron can be used excellently in everyday life and retain their elegant and unique appearance. Suitable as a document folder for A4 + documents.