For fill-in reactions only: T4 DNA Polymerase can be used in NEBuffers 1.1, 2.1, 3.1 and CutSmart® Buffer as well as NEBuffers 1-4 and T4 DNA Ligase Reaction Buffer. For blunting reactions requiring removal of overhangs: T4 DNA Polymerase can be used in NEBuffers 1.1, 2.1, and CutSmart Buffer as well as NEBuffers 1, 2, and 4 and T4 DNA Ligase Reaction Buffer. NEBuffers 3.1 and 3 are not recommended when overhang removal is required. Supplementation of dNTPs is required for all blunting reactions. Optimal activity is observed in NEBuffer 2.1. BSA supplementation is recommended when using a buffer that does not already contain BSA.