Curves: single-stellar mass vs K_s-band magnitude (K_s-mag) for three different central H fractions (X_c = 0.69, X_c = 0.35, and X_c = 0.01) using solar metallicity MIST (black) and M24 (blue) grids of non-rotating stellar models. Two-dimensional histogram: 2MASS K_s-mag vs. eclipse-inferred primary mass for the 5243 targets that satisfy the previously discussed radius ratio and surface brightness ratio cuts, have an eclipse-inferred primary mass, and have a 2MASS K_s-mag measurement.