This article describes the new frontier in spatial power combiners showing the performances of three amplifiers employing the spatial combining technique,two prototypes in the X-Band and one in the Ka-Band.Such Spatial Power Amplifiers has been developed using the design approach described.They belong to the Single Waveguide group in the Spatial Power Combiners family,thus a WR90 and a WR28 waveguides are employed.Very good performances are obtained from prototypes,hence return losses are best than 10dB and the Ka-Band amplifier has carried out 50W in continuous wave.Design approach deals with the Electromagnetic,Thermodynamic and Structural Mechanics features.