MOLESKINE
The Moleskine notebook is the heir and successor to the legendary notebook used by artists and thinkers over the past two centuries: among them Vincent van Gogh, Pablo Picasso and Ernest Hemingway.
Sizing:

Pocket Notebooks = 9 x 14cm (approx. A6 for product filtering)
Large Notebooks = 13 x 21cm (approx. A5 for product filtering)
Extra Large Notebooks = 19 x 25cm (approx. B5 for product filtering)