Two-fuel two-stage progressive or modulating (for gas) or two-stage (diesel) burners with reduced nitrogen oxide (Low NOx) emissions of the RLS / M MX (MZ) series are specially designed for use in heat generators for various purposes of medium and high power. The ability to work in modulation mode (on gas) guarantees precise maintenance of the controlled parameter at a given level with a sufficiently high efficiency throughout the entire modulation range.