By now, mobile 3D interaction is often limited to simple multi-touch input on standard devices and less expressive or hard to use. We present the concept of mobile dual-display devices that can be folded for the exploration of 3D content. We examine different display modes and introduce new presentation and 3D interaction techniques that make use of the special form factor and the added input modality of folding two displays. In particular, we also consider the advantages of our proposed device for head-coupled perspective rendering -- virtually extending the view and providing independent perspectives for two users.