(@giavalisco04; @bouwens09), respectively. The colors plotted in Figure \[fig-dropouts\] are synthetic colors integrated from the best-fit FAST templates. About 57% of the galaxies in the $3.0 \leq z < 4.0$ mass-selected sample have colors that satisfy either the $U$- or the $B$-dropout color criteria (gray shaded area in Figure \[fig-dropouts\]). Of these, three would be selected as $U$-dropouts, and five as $B$-dropouts, based on their observed optical colors. However, $\sim$50% of these UV-selected galaxies are fainter than $r_{\rm tot}=25.5$, which is the observed optical limit of typical spectroscopic samples of LBGs. While the $r_{\rm tot}=25.5$ cut is not relevant to the inclusion of our galaxies in the photometric window, it is relevant when considering our objects in the context of pre-existing LBG surveys.

The rest-frame SEDs of the mass-selected sample at $3.0 \leq z < 4.0$ are shown in Figure \[fig-restframe\], together with the median rest-frame SED from the data (solid blue curve) and the median best-fit templates from FAST (green and red solid curves). Figure \[fig-restframe\] clearly shows the strongly-suppressed emission and the flatness of the spectrum in $F_{\lambda}$ in the rest-frame UV, as well as the strong Balmer/4000 Å breaks in the rest-frame optical for the typical very 