From Hobonichi's website:
This notebook has Tomoe River paper, opens completely flat, and contains graph paper divided into 4 colors.
The Tomoe River paper is the same thin, durable paper as that used in the Hobonichi Techo. This allows the 288-page book to stay at a mere 10mm thick, giving you plenty of room to fill to your heart’s content.
The 3.7 millimeter graph paper is also the same as that of the Japanese-edition Hobonichi Techo Original. The color of the ink on the page changes every 72 pages (red / blue / green / purple), making it easy to split the book into several themes or use the colors as a way to more easily find old entries.
The notebook size is the same as the A5 Cousin, which makes it compatible with any of the Cousin’s Hobonichi Techo covers. The cover is great for storing items like pens or sticky notes, and provides a very convenient user experience.