Offset between the BAT position and the counterpart position as a function of the detection significance. A few values are far from the overall distribution either because they are in crowded fields and their reconstructed sky position is contaminated by the PSF of the nearest sources (red stars) or because they are extended sources (green circles). The solid blue line represents the fit to the data (excluding the outliers) with a power law. The dashed red line represents the 95% containment radius.