When you want a bit more protection against the chill and to keep your comfort, look no further than the 2XU Aero Long Sleeve. Constructed with X-Vent technology, this double-knit crew is lightweight, sweat-wicking, and breathable so you are able to perform with ease. It works great as a single layer and base layer when the weather gets fierce. The 360 reflectivity gives you visibility in those low-light conditions.