Diethylgermanium-diphenylsilicon oxide [(Et2Ge)O(Ph2Si)O]2 has been prepared by reaction of diethylgermanium dichloride and diphenyldihydroxysilane. Spectra and X-ray analysis showed the presence of a puckered eight-membered silicon-germanium-oxygen ring. The ethyl groups of the germanium atoms are disordered. A procedure is proposed for eight-membered rings with low symmetry to obtain a classification into clearly explaining ring forms based on exact or approximated planes put through as many ring atoms as possible. All of the 42 published eight-membered rings with silicon or germanium and oxygen, nitrogen or carbon could be classified by this method.