Q5® Hot Start High-Fidelity DNA Polymerase is a high-fidelity, thermostable, hot start DNA polymerase with 3´→ 5´ exonuclease activity, fused to a processivity-enhancing Sso7d domain to support robust DNA amplification. The addition of an aptamer-based inhibitor allows room temperature reaction setup. With an error rate ~280-fold lower than that of Taq DNA Polymerase, Q5 Hot Start High-Fidelity DNA Polymerase is ideal for cloning and can be used for long or difficult amplicons. Q5 Hot Start High-Fidelity DNA Polymerase is supplied with an optimized buffer system that allows robust amplification regardless of GC content. The 5X Q5 Reaction Buffer contains 2 mM Mg++ at final (1X) reaction concentrations and is recommended for most routine applications. For GC-rich targets (≥ 65% GC), amplification can be improved by the addition of the 5X Q5 High GC Enhancer. Q5 Hot Start High-Fidelity DNA Polymerase is unlike typical, lower fidelity PCR enzymes. To determine the optimal annealing temperatures for a given set of primers, use of the NEB Tm Calculator is highly recommended.