Intracluster medium gas fraction at R₅₀₀ obtained from our reference hydrostatic-based mass model (blue squares) as a function of the total mass corrected for non-thermal pressure support (see Sect. 4.3). The red points show the gas fraction obtained using the Planck PSZ2 masses estimated from the Y_SZ − M₅₀₀ relation (Planck Collaboration XXVII 2016), whereas the green triangles show the gas fraction that would be obtained by correcting the PSZ2 masses with a uniform mass bias 1 − b = 0.58 ± 0.04 (Planck Collaboration XXIV 2016). The dashed magenta line and shaded area represent the universal gas fraction estimated in Sect. 3.1.