X17 - The only "real ring notebook" because only X17 uses real rings! X17 Notebook: Your notebook for everything. Each X17 Notebook can hold two to four insert booklets. We currently have 15 different types of insert booklets for each format size and are continually adding more insert booklets to our selection. That's why an X17 Notebook can be used for anything! For example, you can use it as a: