A microwave arrangement for affixing the toner onto a printing material by heating, wherein a resonator chamber for feeding printing material therethrough includes at least one element, which extends into the resonator chamber and is used for tuning the resonance state in the resonator chamber. The element includes at least a first portion of a material with properties that essentially do not absorb the microwave radiation and a second portion of a material with mechanically stable properties and a slightly higher absorption of the microwave radiation than the first portion.