  We present Hubble Space Telescope observations of six binary transneptunian
systems: 2000 QL251, 2003 TJ58, 2001 XR254, 1999 OJ4, (134860) 2000 OJ67, and
2004 PB108. The mutual orbits of these systems are found to have periods
ranging from 22 to 137 days, semimajor axes ranging from 2360 to 10500 km, and
eccentricities ranging from 0.09 to 0.55. These orbital parameters enable
estimation of system masses ranging from 0.2 to 9.7 x 10+18 kg. For reasonable
assumptions of bulk density (0.5 to 2.0 g cm-3), the masses can be combined
with visible photometry to constrain sizes and albedos. The resulting albedos
are consistent with an emerging picture of the dynamically "Cold" Classical
subpopulation having relatively high albedos, compared with comparablysized
objects on more dynamically excited orbits.
