parallel field is constant out to $R_{200}$. The upper and lower estimates were obtained by integrating along the lower and upper error bars of the corrected profile, out to the upper and lower bounds of $R_{200}$, respectively. The large range in the abundance of UDGs in Abell S1063 is a result of its $R_{200}$ value being poorly constrained.

Our new estimate for the abundance of UDGs in Abell 2744 of $1351^{+387}_{-379}$ is slightly lower, but consistent with, our previous result of $1961 \pm 577$ [@janssens2017]. This is due to our revised UDG selection, most notably that UDGs in Abell 2744 fainter than the 50% completeness limit of $\langle\mu\rangle_{e,F814W} = 26.9~\mathrm{mag}~\mathrm{arcsec}^{-2}$ were excluded from the estimate in this analysis. The mass of Abell 2744 has been slightly lowered in this analysis as well. In [@janssens2017], an ensemble mass estimate from lensing and dynamical studies was used, but here we only use a lensing mass estimate to be consistent with the other five clusters studied.

In Figure \[fig:abundance\], we update the UDG abundance halo-mass relation including all six FF clusters, along with the abundances in other systems from the literature. [@vdb2016] investigated the UDG populations in 8 clusters at redshifts $0.044 < 