SIXS Carbon Underwear long sleeve turtleneck t-shirt that is breathable and thermoregulating in any weather conditions. The long sleeve hugs every part of the arm to keep the skin fresh and lies between the skin and a top garment. It also slightly protects against cool drafts if a short-sleeve top garment is worn. Lastly, the mock turtleneck collar protects the throat from sudden temperature changes and cool drafts.