We recommend use of included NEBuffer r1.1 for RNA digestions with RNase 4 Digestion and 3′ End Repair Mix following our recommended digestion protocol. The 3′ end repair activity of T4 polynucleotide kinase requires magnesium for efficient phosphate removal. However, it is noteworthy that like RNase A, RNase 4 does not require magnesium for endoribonuclease activity.