How many tetrahedra are needed in the ring to achieve a pore size of 6 Å?
Dynamic figure 29.1 The ring sizes in zeolites and the number of tetrahedra forming them ranges from 4 to 14; the associated pore or window dimension increases from under 3 Å to 10 Å.

4-ring
< 2.5 Å
Zeolite SOD
< 2.5 Å
Zeolite SOD