Lightweight and breathable, 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.
This sweat-wicking and heat-regulation mechanism also works well on an indoor trainer, where the baselayer will keep you cooler than a jersey but drier than the no-shirt option.
So light you won't know you're wearing it, and it can improve safety outcomes! In the very unfortunate event that you find yourself doing a close-up road inspection, the humble base layer protects your skin from nasty road rash.
These are tight-fitting to go nicely under your lycra, we recommend your normal size.