This is a single notebook with high-quality Kokuyo THIN fountain pen paper and a 3mm light gray grid. Use it to add 80 more pages of space to your B6 "Mini" Jibun!
From the manufacturer:
For better searchability, write the dates and titles to the left of the vertical line. You can use this notebook as a daily journal, a place to jot down ideas, a collection list, a reading journal, notes for sketches, meeting minutes, or so many other things.