For fill-in reactions only: DNA Polymerase I, Large (Klenow) Fragment can be used in NEBuffers 1.1, 2.1, 3.1 and CutSmart® Buffer as well as NEBuffers 1-4 and T4 DNA Ligase Buffer. For blunting reactions requiring removal of overhangs: DNA Polymerase I, Large (Klenow) Fragment can be used in NEBuffers 2.1, 3.1, and CutSmart Buffer as well as NEBuffers 2, 3, and 4 and T4 DNA Ligase Buffer. NEBuffers 1.1 and 1 are not recommended when overhang removal is required. Optimal activity is observed in NEBuffer 2. Supplementation of dNTPs is required for all blunting reactions. It can also be used in Cutsmart Buffer. To see its % functional activity in Cutsmart, and that of other DNA modifying enzymes in the cloning workflow, refer to the Activity of DNA Modifying Enzymes in CutSmart® Buffer chart.