RNA molecules, including siRNA molecules and related control, trackability and exaequo agents with specific stability modifications are provided. These molecules are particularly advantageous as transfection control reagents. The molecules include first and second 5′ terminal sense nucleotides with 2′-O-alkyl groups and a label on the first 5′ terminal sense nucleotide, in conjunction with at least one additional 2′-O-alkyl pyrimidine modified sense nucleotide, and either: (i) at least one 2′ fluoro modified pyrimidine antisense nucleotide and a phosphorylated first 5′ terminal antisense nucleotide; or (ii) a first and second 5′ terminal antisense nucleotide with 2′-O-alkyl modifications and at least one additional 2′-O-alkyl pyrimidine modified antisense nucleotide.