These are hydration backpacks.
They're for EFFICIENCY.
The Big Bang Theory Season 10, Episode 20
and its quantum EFFICIENCY
is off the charts.
The Big Bang Theory Season 12, Episode 7
You cannot beat
the thermal EFFICIENCY
of the C3.
Breaking Bad Season 2, Episode 10
Allowed me to correct
for the observational EFFICIENCY.
The Big Bang Theory Season 3, Episode 4