Optimal activity is seen in NEBuffer 2. Klenow Fragment (3'→5' exo-) is active in NEBuffers 1.1, 2.1, 3.1 and CutSmart, as well as NEBuffers 1-4, when supplemented with dNTPs (not included). 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.