This is the Wittmann Materassi Matteo Thun. You can configure it in a bunch of different ways. Backrests or not. Armrests or not. Do whatever you like.
“A set of furniture which places flexibility first. An innovative, patented, plug-in system for arm-rests and back-rests allows for individual design requirements. The diversity of possible combinations and coverings gives Materassi a completely personal touch. ”
This is a pretty cool idea. I would totally buy one if the price is right, and if I had a bigger apartment.
Here is the link to their site.