Cluster mass scale determined by CMB lensing. We show the ratio of cluster lensing mass, M_lens, to the SZ mass proxy, M_Yz, as a function of the mass proxy for clusters in the MMF3 2015 cosmology sample. The cluster mass is measured through lensing of CMB temperature anisotropies in the Planck data (Melin & Bartlett 2015). Individual mass measurements have low signal-to-noise, but we determine a mean ratio for the sample of M_lens/M_Yz = 1 / (1−b) = 0.99 ± 0.19. For clarity, only some of the error bars are plotted (see text).