for ULXs to be massive stellar remnant BHs. Yet, population studies of the HMXB population of the local universe has also revealed an unbroken power-law slope in the XLF up to $\sim2 \times 10^{40}$ erg s$^{-1}$ (e.g., @2003MNRAS.339..793G; @2011ApJ...741...49S; @2012MNRAS.419.2095M). This continuation indicates that the majority of ULXs with $L_\mathrm{X} < 2 \times 10^{40}$ erg s$^{-1}$ are likely to be HMXBs with a stellar-mass BH accreting at around or above the Eddington limit. Many studies have been undertaken to obtain the mass of the putative BH contained in ULXs. Such methods include: studying the ULX optical counterpart (e.g., @2006IAUS..230..293P; @2009ApJ...697..950K; @2011ApJ...728L...5C; @2011ApJ...737...81T; @2013ApJS..206...14G); from X-ray analysis, using either spectral fitting (e.g., @2003ApJ...585L..37M; @2009MNRAS.397..124G; @2010MNRAS.402.2559C; @2011ApJ...734..111D; @2012ApJ...752...34G; @2013arXiv1310.0745B), the luminosity-temperature relation (e.g., @2003ApJ...585L..37M; @2009MNRAS.397..124G; @2009ApJ...692..443S; @2011ApJ...743....6S), quasi-periodic oscillations (e.g., @2003ApJ...586L..61S; @2007ApJ...660..580S; @2013MNRAS.tmp.2483C), or X-ray variability (; @2009MNRAS.397.1061H; @2013MNRAS.tmp.2522D). In those cases where candidate radio counterparts have been identified, attempts have been made to obtain the BH mass using the Fundamental Plane of accreting BHs (e.g., ; @2011IAUS..275..325C; @2011AN....332..379M; @2012Sci...337..554W; @2013MNRAS.436.1546Ma; @2013MNRAS.436.3128Mc). The Fundamental Plane is a correlation between 2–10 keV X-ray luminosity, 5 GHz radio luminosity, and BH mass that holds for sub-Eddington accreting BHs in the low/hard X-ray state and 