This zipper case is a collaborative product with Japanese brand called "Four ru of", featuring items that utilize original textile paper cloth that has a paper-like texture. We created this passport size zipper case specifically for inserting into your passport sized TRAVELER'S notebook to increase storage capacity. The zipper case functions as a pocket on one side that is sealed with a zipper, allowing you to keep money and coins turning your passport size TRAVELER'S notebook into a wallet. On the other side there is a business card sized slip that makes it simple to carry all of your receipts and small notes. The natural blue colored material that is used is a very thin cotton combined with a special glue which gives the outside a thin, paper like texture that is durable and will accompany you through many travels. This blue color was created to be lighter than the blue notebook so it stands out when you combine it. Just like the TRAVELER'S notebook, this material was chosen because its wrinkles and maturation over time will complement your notebook.