Men's Ocean Baselayer
Lightweight and breatheable, the ocean baselayer dissipates sweat, creating a pocket of air between the fabric and your skin. This helps to regulate your body temperature by keeping you warm and dry.
The baselayer's sweat wicking and heat regulation also works well on an indoor trainer, where the baselayer will keep you cooler than a jersey but drier than no-shirt
I don't reccomend trying this at home...but in the unfortunate event that you find yourself doing a close-up road inspection, the humble baselayer will protect your skin from nasty grazing!
All that, and it's so light you wont even know you're wearing it!
Size reccomendation: I'd reccomend your normal size. They are tight fitting. Chris (pictured) is wearing a size Large.