Rietveldrefinement of synchrotron X-ray powder diffraction data of SSZ-16 showsthat this zeolite is the aluminosilicate analogue of SAPO-56 (AFX).SSZ-16 contains a three-dimensional pore system with pores boundedby eight tetrahedral atoms, and is a member of the ABC... type ofzeolites with an AABBCCBB... layer sequence. There is a very goodfit between the size of the organic structure-directing agents usedduring the zeolite synthesis and the size of the large cages ofSSZ-16.