  Using the absolute detection calibration and abundant detections of the OSSOS
(Outer Solar System Origin Survey) project, we provide population measurements
for the main Kuiper Belt. For absolute magnitude $H_r<8.3$, there are 30,000
non-resonant main-belt objects, with twice as many hot-component objects than
cold, and with total mass of 0.014 $M_\Earth$, only 1/7 of which is in the cold
belt (assuming a cold-object albedo about half that of hot component objects).
We show that transneptunian objects with $5.5 < H_r < 8.3$ (rough diameters
400--100~km) have indistinguishable absolute magnitude (size) distributions,
regardless of being in the cold classical Kuiper belt (thought to be
primordial) or the `hot' population (believed to be implanted after having been
formed elsewhere). We discuss how this result was not apparent in previous
examinations of the size distribution due to the complications of fitting
assumed power-law functional forms to the detections at differing depths. This
shared size distribution is surprising in light of the common paradigm that the
hot population planetesimals formed in a higher density environment much closer
to the Sun, in an environment that also (probably later) formed larger (dwarf
planet and bigger) objects. If this paradigm is correct, % << BG added clause
our result implies that planetesimal formation was relatively insensitive to
the local disk conditions and that the subsequent planet-building process in
the hot population did not modify the shape of the planetesimal size
distribution in this 50--300~km range.
