X-ray-to-optical flux ratio as a function of Gaia colors showing the position of the eROSITA WD subsample (circles) and confirmed period-bouncers (triangles) detected in eRASS:4. The bona fide period-bouncers used to establish the selection cuts are highlighted in black. See text for the justification of the selection cut lines. The members of the eROSITA WD subsample that fulfill the X-ray luminosity and Gaia colors selection cuts are highlighted in yellow; the ones that do not are in pink. Black circles are placed around possible resolved binaries in the eROSITA WD subsample.