Dry for the long haul.
Although it seems counterintuitive, base layers are essential even while riding in warmer months. Their main purpose is to keep moisture off of the skin, which grows in importance on chilly spring/summer mornings. For this reason, Giordana created the Mid-Weight Polypropylene Sleeveless Base Layer. It adds a little more warming protection than Giordana's lightweight base layer, yet it is not so warm that you'll be shedding layers mid-ride.
For the construction of the base layer, polypropylene was selected over the standard polyester for both its moisture management and durability. Polypropylene and polyester are both polymers, meaning that they're both essentially plastics. However, where they differ is that polypropylene is hydrophobic to that point that it's unable to absorb water. And, as a result, it spreads moisture out over a larger surface area, which rapidly accelerates evaporation. So, in short, these fibers ensure that your torso will remain dry over the long haul.
Coupled with the base layer's next-to-skin fit, flatlock seams ensure that you won't chafe while you ride.
The Giordana Mid-Weight Polypropylene Sleeveless Base Layer - Men's is available in the color White and in four sizes from Small to X-Large.