Further, the curved E Ink display, as Yanko Design reported, has the same width as an A4-sized paper and comes with a round knob on either side which can be used to roll the page up and down ...

More specifically it is a 3mm-radius curved display that the Ledger Stax comes with. Measuring the size of a credit card, the Ledger Stax is also extremely handy and can be carried almost anywhere.