Ito el al. have synthesized dumbbell RNA's just as had been done before for DNA's by Breslauer et al. (Biochemistry, 1989, 28, 268-273). The utility of this dumbbell RNA's is in RNA interference, they are proven to be more stable to enzymatic degradation and at the same time offer longer RNAi acitivity since the shape does not offer loose ends for enzyme degradation. They have synthesized and compared four different sized dumbbells, that is, Db-15, Db-19, Db-23, Db-27, where the number refers to the size of the double stranded A-type region, the hairloops at the ends of the dumbells are of 9nt size.