Cyclomethicone is a generic name for several cyclic dimethyl polysiloxane compounds ... it refers not only to octamethylcyclotetrasiloxane (D4), but also to cyclotrisiloxane (D3), cyclopentasiloxane (D5), cyclohexasiloxane (D6), and cycloheptasiloxane (D7), i.e. compounds of the general formula (CH3)2n-(O)n-(Si)n where ...