The Multi Fold Out Ruler from Midori is a compact addition to your pencilcase that can measure up to 16 cm when opened. It's shorter than a pen when folded which makes it super portable.
There are holes every 10 mm, which is convenient for marking.
It clicks every 15 degrees so you can measure the angle.
Also available in a 30cm version.
A little reminder to drink some water! 💧