  We report observations of nine MBCs or candidate MBCs, most of which were
obtained when the targets were apparently inactive. We find effective nucleus
radii (assuming albedos of p_V=0.05+/-0.02) of r_n=(0.24+/-0.05) km for
238P/Read, r_n=(0.9+/-0.2) km for 313P/Gibbs, r_n=(0.6+/-0.1) km for 324P/La
Sagra, r_n=(1.0+/-0.2) km for 426P/PANSTARRS, r_n=(0.5+/-0.1) km for
427P/ATLAS, r_n<(0.3+/-0.1) km for P/2016 J1-A (PANSTARRS), r_n<(0.17+/-0.04)
km for P/2016 J1-B (PANSTARRS), r_n<(0.5+/-0.2) km for P/2017 S9 (PANSTARRS),
and r_n=(0.4+/-0.1) km for P/2019 A3 (PANSTARRS). We identify evidence of
activity in observations of 238P in 2021, and find similar inferred activity
onset times and net initial mass loss rates for 238P during perihelion
approaches in 2010, 2016, and 2021. P/2016 J1-A and P/2016 J1-B are also found
to be active in 2021 and 2022, making them collectively the tenth MBC confirmed
to be recurrently active near perihelion and therefore likely to be exhibiting
sublimation-driven activity. The nucleus of 313P is found to have colors of
g'-r'=0.52+/-0.05 and r'-i'=0.22+/-0.07, consistent with 313P being a Lixiaohua
family member. We also report non-detections of P/2015 X6 (PANSTARRS), where we
conclude that its current nucleus size is likely below our detection limits
(r_n<0.3 km). Lastly, we find that of 17 MBCs or candidate MBCs for which
nucleus sizes (or inferred parent body sizes) have been estimated, >80% have
r_n<1.0 km, pointing to an apparent physical preference toward small MBCs,
where we suggest that YORP spin-up may play a significant role in triggering
and/or facilitating MBC activity.
