These neoprene shirts are like a wetsuit top. Made from Neoprene, most of them have a smooth skin to stop wind penetration in the core areas. They then offer super stretch material in the arms and where you need it to increase your range of motion.
Great by themselves or as a layer to add warmth under your wetsuit.
I use these neoprene shirts a lot as they are very easy to get on and off and really keep my core warm!