Phusion DNA Polymerase is supplied with standard 5X Phusion HF Buffer, as well as 5X Phusion GC Buffer, which can be used for complex or GC-rich templates. Each of these buffers contains MgCl2 (1.5 mM at the final [1X] reaction concentration). Reactions can also be optimized using the provided DMSO or MgCl2 solutions.