Apart from the fact that the notebook is for repeated use and you can easily clean it using a wet cloth, the clever thing is that it comes with an app that let you take images and store them as pdf files in your mobile phone.
I bought the Elfin notebook 2.0, the English version, from GEECR, click the image above if you are interested in getting one. They sell it in two different sizes A5: 148 x 210, agenda type and B5: 176 x 250, traditional notebook, both smaller than an A4: 210 x 297, normal sheet of paper. That means that they are both practical and not too big for you to carry it around the classroom.
GEECR sends the new Elfin 2.0 version with the pilot Frixion pen (see right picture below). Consider that the old Chinese version of Elfinbook 2.0 used a different pen (right) with different ink refills, that are slightly bigger. So, make sure what kind of ink refills you need for the pen you are using.