A self-bonding, heat-vulcanizable silicone rubber composition comprising (a) an organopolysiloxane polymer of the formula RaSiO(4 a)/2, (b) a curing catalyst, and (c) an additive selected from cyanurates, isocyanurates, silyl-cyanurates and silylisocyanurates, where R is selected from monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals, a varies from 1.95 to 2.01. There may also be present in the above composition a process aid and a filler, as well as other ingredients.