The kit consists of two modules: Phanta Max Super-Fidelity DNA Polymerase amplification module and ClonExpress rapid cloning module. The ultra-fidelity of Phanta Max can significantly reduce the possibility of unexpected mutations during amplification of up to 20 kb in length. The ClonExpress rapid cloning module allows homologous recombination reactions to replace the conventional annealing ring-forming reactions, requiring much less template and more flexible primer design strategy. Due to the efficient seamless splicing of the two PCR products by ClonExpress technology, the kit can complete the two separate sites mutation by single amplification reaction. DpnI digested products of the specific amplicons can be directly added into recombination reaction without purification. Highly optimized reaction buffer, fast operating procedures and amazing site-directed mutagenesis efficiency make Mut Express II Fast Mutagenesis Kit V2 the preferred kit for DNA site mutation.