  One of the most striking and curious features of the small Kuiper Belt Object
(KB), Arrokoth, explored by New Horizons, is the bright, annular neck it
exhibits at the junction between its two lobes. Here we summarize past reported
findings regarding the properties of this feature and report new findings
regarding its dimensions, reflectivity and color, shape profile, and its lack
of identifiable craters. We conclude by enumerating possible origin scenarios
for this unusual feature. New results include a new measurement of the observed
neck area of 8+/-1.5 km2, a total neck surface area of 32 km2, a 12.5:1 ratio
of neck circumference to height, a normal reflectance histogram of the observed
neck, and the fact that no significant (i.e., >2 sigma) color units were
identified, meaning the neck's color is generally spatially uniform at the 1.5
km/pixel scale of the best color images. Although several origin hypotheses for
the bright material in the neck are briefly discussed, none can be conclusively
demonstrated to be the actual origin mechanism at this time; some future tests
are identified.
