This is a Kumon textbook binder. It can be used to store and organize Kumon worksheets. The thickness can be adjusted for 200 sheets or 400 sheets. When you start learning, it's difficult to keep track of the vast amount of worksheets, but you don't want to throw them away... so you can file them by subject. Also, for children who have advanced to higher-level materials, their own completed worksheets become the best reference books. Filing them by subject is also a great way to remember old grammar and other concepts when they get stuck. It fits exactly 200 or 400 sheets, without creating wasted space. It's easy to put on a bookshelf. The old version of the binder has been renewed, with improvements to the material's firmness, texture, and the design of the string. The usability remains the same, but the durability has been increased. The price has also been slightly changed accordingly. 《Material》Paper Please also take a look at ↓ #Kumon related, children's enjoyable collection If you have any questions, please feel free to comment.