“mako dual circuit” is a special version of the modular, compact mako add-on cooler with two cooling or temperature control circuits which can be controlled independently from one another. It is particularly suitable for the separate cooling of fibre lasers and optical systems. The required cooling capacity is provided by a refrigeration circuit via a refrigeration circuit in a central water tank. The second water circuit provides the supply for the optical system. The temperature is controlled separately – by a modulating valve and a heater. The heating capacity is adapted to the application at hand and is approx. 500 W, which means that a variable control range from 20°C to 25°C can be covered, for example, for the optical system.