Examples of common masks. From top to bottom, the masks correspond to those used for analysing temperature maps, polarization represented by the Stokes Q and U parameters, and E-mode polarization data, at a resolution N_side = 128. From left to right, full-mission, HM, and OE masks are shown. Note that the masks for E- and B-mode analysis are extended relative to those derived for Q and U studies, in order to reduce the reconstruction residuals.