David Millar says:
"This is a microfibre polyester made as light and soft as
possible. Its hydrophilic outer layer wicks moisture off the skin
to the jersey yet doesn't absorb moisture along the way. We made it
a perfect weight so that when paired with the 1.21 jersey you end
up with the combined weight of a normal looking jersey only with
much better comfort and moisture management.
Contrary to the subdued colours of the outer layer, we decided
to make the base layer a bit more colourful, much the way a
gentleman may choose the inner lining of his suit to contrast with
the outside. In tailoring this is called a reveal, a flash of
colour occasionally glimpsed that shows there's something more
going on than at first perceived.
The coloured design is taken from parametric patterns created
from the data (a combination of my heart rate, watts, speed,
distance, etc.) of my final race: the 17th stage at the 2014 Vuelta
The neck is a little rounder than normal, more like a vest than
a t-shirt. This compensates for the higher necks of the 1.21 and
1.61. I chose a sleeveless cut as this and the 1.21 jersey are
designed to be used together. Sleeves on an undershirt can often be
more uncomfortable with a short-sleeve jersey."