This is a general chart of notebook sizes. Inserts and notebooks can vary in fit depending on the thickness of the book and added embellishment.
FN Small: 3.5 x 5.5
FN Large: 4.75 x 7.5
FN Signature: 4.25 x 6.5
Moleskine Cahier: 5 x 8.25
A5 Modified: Fits the Jibun Techo, 5.125 x 8.25