This is a binder for Kumon educational materials. It's a ring binder, so the pages won't close on their own. It's very convenient for studying while looking at the origins and grammar points of things you haven't memorized yet. The worksheets you've solved yourself become the best reference books. Also, the material is sturdy, so your worksheets won't get creased when you carry them around. Material: PP Because of its thickness and considerable weight, this will be sent via non-standard mail or Nekopos, and the shipping cost is relatively high. If you purchase several at once and have them shipped together, the shipping cost will change, so please consult with me. I will ship them in the most affordable way. Please take a look here: ↓ #Kumon related, children's enjoyable collection If you have any questions, please feel free to comment.