Abstract: Products of the reaction of about 30 to 90 parts by weight of a compound of formula (I) ##STR1## wherein R.sub.1 and R.sub.2 are each alkyl radicals having up to 8 carbon atoms at least one of which is branched on the alpha carbon, and R.sub.3 and R.sub.4 are each hydrogen or an alkyl radical having up to 18 carbon atoms, and about 70 to 10 parts by weight, respectively, of a secondary or tertiary phosphite are useful for stabilizing polyolefins against degradation by heat and ultraviolet radiation and for rendering polyolefins dyeable by chelatable dyes such as aromatic ortho hydroxy azo dyes.