Synonyms: 3,9-bis[2,4,6-tris(1,1-dimethylethyl)phenoxy]-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane;AT 633;Bis(2,4,6-tri-tert-butylphenyl) pentaerythritol diphosphite;Ultranox633;3,9-bis(2,4,6-tri-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane;2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis[2,4,6-tris(1,1-dimethylethyl)phenoxy]-;