Impact of the XMM-Newton instrumental background on the derived temperature (left) and iron abundance (right) in the outer regions of the clusters. The black squares show the reference measurements with no systematics considered. The red dots were derived using a lower instrumental background, while the blue stars were derived using an overestimate of this component, as described in the text. The pink shaded areas represent the dispersions associated with different XRB parameters within the same radial bin.