The twin ring binding is fantastic on these books. It's strong, sturdy, and come in a variety of colors. While we're talking about colors and variety, I'll also mention that the books come in graph, blank, and lined varieties. The graph books have white binding, the blank books have black binding, and the lined books are available with blue, green, red, or yellow binding. Plenty of choices, all for $4.35.
Finally, the size is one of my favorites — slim B5. It's tall and slender, which is perfect for me when writing.
The paper
I was surprised by the quality of the paper in relation to the price, which is a good thing.
The paper is very smooth with every pen I've tried. It's a pleasure to write on, just like other Apica papers I've tried. The paper is 70 gsm weight, which is barely good enough for fountain pens. I say barely, but it actually handled everything I tried with flying colors. Each paper is different, and I've used other 70 gsm papers that didn't perform as well as this one.