I am proud to present Apica's line of "Premium CD" notebooks. Please don't confuse these with their regular CD notebooks - the Premium line is a whole different class, and the quality reflects it.
Indeed, they really are "premium". The paper is super-smooth and fountain pen friendly, and because of its excellent thread binding, the book is sturdy, easy to open, and lays flat.
These are easily as high quality as any high-end notebooks from anyone else.
This is the plain paper version. The following sizes are available:
A4: 210 x 297mm
B5: 182 x 257mm (note that this is "JIS-B" size. The more common ISO size is 176 x 250mm)
A5: 148 x 210mm
All sizes have 96 sheets/192 pages.