And I mean perfect. At every level of the meaning of the word, they are perfect - the definition of an ideal type / excellent beyond theoretical improvement / exactly fitting a certain need / entirely without flaws...
As an example, let's look at the 'Aufschreiben' diary above. It is a pocket diary, so you're supposed to carry it around with you. For this reason, it's a nice slimline 9.5cm wide.
Aufschreiben is German for 'to write down', so you're supposed to take notes in it. For this reason, it has a weekly notebook format.
And since you're supposed to write down all of the extemporaneous tid bits of life as the diary accompanies you, it even has a pen loop...and a pen.
And because when one of these spontaneous 'moments' arises, you don't want to be flicking frantically to find the right page, it has page markers...two of 'em, so you know where you are.
And because a diary - where you write down everything you do in your life - is more or less a paper extension of yourself, it should look good, suit your taste, be well made and not a bulk standard 'thing' which happens to say 2011 on the cover. Check, check and check!
The pages have silver or gold edging, the colours are beautiful and it feels nice...no, scrap that... not nice...perfect! Check out further instances of stationery beyond improvement here.