The figure shows a schematic depiction of the algorithm employed in calculating the pore sizes listed in Table 2. The pore size is defined through the radius of the largest spherical cargo capable of passing through the final structure resulting from a simulation of a system of Nsp1-FGs. A search for the largest cargo starts on one side of the system, the latter shown in grey. The cargo (black sphere) of a certain size moves towards the other side while the algorithm probes if the cargo can pass. The panel at right illustrates what is measured by the algorithm, namely the radius of the largest cargo that can pass through along a probing direction. As shown in this panel, there are two bottlenecks, the second smaller one of which determines how large a ball can pass through the obstacles and, therefore, characterizes the pore size of obstacles.