EPICENTRE’s MasterAmp™ Extra-Long PCR Kit allows successful and accurate one-step amplification of DNA sequences from 20 kb to about 40 kb in an easy to optimize format. The kit contains the MasterAmp Extra-Long DNA Polymerase Mix along with 9 MasterAmp Extra-Long PCR 2X PreMixes containing dNTPs, buffer, and varying amounts of MgCl₂, and the MasterAmp™ PCR Enhancer with Betaine. For each new set of template and primers perform a PCR with the MasterAmp™ Extra-Long DNA Polymerase Mix and 9 PreMixes to find the optimal PreMix, and then perform subsequent amplifications with the same template and primer pair using that PreMix. Benefits include one-step optimizations of extra-long PCR reactions and no need for “hot-start”.