The close similarity between these two spherical cups is based on a set of moving compressive bars that are connected together to form a three dimensional mechanism. These two deployable structures are capable of expanding up to several times of their packaged size, when their bars are rotated relative to one another.
In the first spherical cup, all the bars meet with one another once the structure contracts from a dome-like shape to a completely compact bundle. This leads to the
structure that corresponds to the most efficient folding configuration and maximum expansion conditions. The first cup is ideal for the purposes where compact packaging is essential. The second cup cannot be folded up entirely. The second cup cannot be folded up entirely.
The joints are made of aluminum sheet and provide one degree of freedom. The first cup has less joint types (one type) than the second cup (four types). This can facilitate the process of installation.