The Phusion enzyme is the same, albeit now manufactured by NEB. However, the hot start mechanism utilized by the Phusion Hot Start Flex DNA Polymerase is different. Phusion Hot Start Flex DNA Polymerase contains an aptamer-based inhibitor, which allows for room temperature reaction set up. Cycling conditions for the Phusion Hot Start Flex DNA Polymerase are based on standard Phusion cycling recommendations. Unlike other hot start polymerases, an extended initial incubation step is not required to activate the enzyme. Phusion Hot Start Flex DNA Polymerase is recommended for any application that requires a hot start, high-fidelity polymerase.