Powerful performance, optimum energy efficiency, pleasant running smoothness, suction aid, safety hose adapter and many other advantages have been taken over from the professionel 3 series. But the highlight is the new "Xtender": If the filter masses are dirty and the water flow decreases, you simply adjust the flow at the rotary knob if necessary. This way, you don't have to intervene immediately and gain a few days until the next cleaning of the filter media. The biological filtration (detoxification) is still maintained by diverted water flow. In terms of color, the professionel 4+ appears in a new guise. The filter is in modern anthracite gray and comes with color-matching hoses, tubes, etc. There are 3 models for aquariums up to 250, 350 and 600 liters. The models 250 and 350 are also available with integrated heater as thermofilter (T). The model 350e offers you additional electronic control also from PC (see professionel 3e).