The invention relates to improved double-stranded RNAi constructs (sometimes referred to as “solo-rxRNA”) and uses thereof. The construct comprises a structure formed in some aspects of the invention by two identical single-stranded polynucleotides, with the structure having two double-stranded stem regions (each having less than 21 base pairs) and a loop or bulge having about 4 to 11 nucleotides on each strand. The construct is resistant to cleavage by Dicer or other Dicer-like RNase III enzymes and is capable of being loaded into a RISC complex to effect RNA interference. In addition, the nucleotides of the present hairpin constructs may be modified to greatly enhance functionality, such as stability and specificity.