The support is called an arm or backrest, depending on whether you put it on its side or back. From a design point of view, they are one and the same. The supports are available in 4 thicknesses, 2, 10, 20, 40, 50 cm. The height of the low armrest (52 cm) is designed so that you can not only rest your arms comfortably on it, but also rest your head on it like a cushion. This allows the armrest to become part of the lying surface, which can be important if the sitting surface itself is not long enough to lie on. This way, you don't waste valuable space with the armrest. If you lie a lot, we recommend the medium height (52 cm) armrest. If you like to curl up in a corner between the backrest and the armrest, go for the tall one (70 cm. The 100 cm high backrest element is very impressive, (only for 2 and 10 cm high backrests) you can create real nooks and crannies, but you will definitely need cushions, because the high vertical lines are not comfortable for your spine.